First, let me say this- "I like T-port spells". They are very magical, very wizardly, very "in genre", imo.
I like a small t-port, ~100 paces or so (well, that's a carry over from 4th ed.) It can be used offensively, defensively, to hide, to avoid detection, to overcome physical obstacles like walls or gates or rivers, to travel in a city without being seen, to spy, to elude a tail- great fun.
For any but a journeyman mage, Mythic Europe should be small. Even if they can't teleport, they should be able to fly or change into a bird or something, and even as fast as a man can run (5 minute mile, 12 mph) and only a lazy 8 hour day, that's 96 miles/160 km/day, as the crow flies. If you bump that to the speed of a horse/hawk, and 12 hrs/day, that can easily quadruple or more, and approach 500 miles/850 km/day. With magic, travel should not be a concern. For magi who specialize in travel, well- we know how specializations work. For wizards who want it to be so, Europe is small.
Now, altho' the book does not address this, there are really 2 kinds of "teleportation". The first is where one where a body (target) is moved from one location to another instantly, but through the intervening distance, just faster than can be seen. The second is where a body/target is relocated from one point to another, without physically traveling through any intervening distance (ala StarTrek).
The difference is obstacles. The former will not get you out of a shut room, unless you can fit up the chimney. The second will get you from deep within one dungeon cell to another, regardless of bars and doors and walls and such. The second will also disappear a mage from manacles or ropes or other restraints, while the first will not. Despite the descriptions of the spells in the book, by my reading the RAW regarding Rego imply that the former is doable, but the latter would require all kinds of Muto and elemental requisites, to pass the target through the intervening obstacles (usually Te or He).
So, with that reading/interpretation, it would not be unreasonable to toss in a magnitude or two of difficulty for the latter type, the "relocate regardless of obstacles" teleportation. The spell descriptions are not specific one way or the other - a 7 league stride still takes you to the location IF there are no obstacles, but does not get you out of chains and the stocks (or the grasp of an ogre?) if that's where you start (and certainly doesn't bring them with, so...)
It's also unclear how "range" works here, because there are 2- the range from the caster to the target (usually "Self"), and the "range" that the t-port then moves the target, which is actually more related to the magnitude of the effect, not the range. You could have a T-port that effects anyone within range of Sight, but only moves them a few paces- but how to guage the overall magnitude...
Anyway...
There is also the problem of targeting, and what happens if something has changed to block the arrival. While some other RPG's are fairly forgiving (and that's what we tend to expect), there's no reason not to house-rule that if something/someone is where you "land", you are screwed. That would only require a Scry spell of equal range to be used ahead of time, which would not preclude T-Porting, but it would rein it in a bit, and make the Teleporting magi think twice about exactly "where" he picks up the arcane connection.
With the advent of Warping, the big T-port spells are less inviting. And the problem of short-longevity Connections adds to the headaches - (as implied above, if the Players have all the Vis they need for a cabinetful of permanant connections, then your problem lies elsewhere.)
As an Ars Storyguide, you have to think like a Wizard, not like a Fighter. Or, at least, like the Characters who will be in the story you tell. If T-porting is ruining your plots, then don't let "travel" be critical to the solution. Any mage will have specialized spells that will solve a particular problem, whether that's travel or food or keeping warm, or bandits or mounted knights or wild animals or faeries or ghosts or demons, or speaking with the dead or seeing into the past or whatever. When you design a "challenge", a scenario, you have to take these solutions into consideration - and plan both for and against them! Let them solve your players' problems on occasion, that's why they have them, to have fun with them! Demon's Eternal Oblivion is no fun if it can't squash a smart-ass demon flat in one casting every now and then! But Teleporting doesn't tell them where the BBEG went, nor what they look like, nor help defeat him when caught up to. Nor does it explain to the two chatting Bishops how the identical odd group was spotted in two different cities on St. Swithian's day...
As far as what "is" vs "is not" an Arcane connection, that's partly up to you, but read the section on page 84.
[i]"...Something... is an Arcane Connection to something else... if the connection was very closely associated with the target, often by being a part of it..."[/i]
Now, in 4th ed, that was a "yes/no" situation- either it was, or it was NOT. In 5th ed, they've given the SG much more wiggle room, by stating that "weak" AC's simply lose their usefulness much faster. So, "water from a body of water" lasts hours, while a "rock from a specific place" lasts for years. (However, I'd rule re that last- [u]if[/u] that place was made of that same rock- like a cave, or a castle- a piece of stone chipped from the very stone of the place. A pebble from a sandy beach might only last months, or less if it was washed there recently by tides or such.)
It's all about how "connected" that connection is to the original thing/place, the target. A sword wielded by a soldier would be a stronger connection than a sword wielded by a farmer. The family heirloom sword of a peasant might be stronger than the personal sword issued to a soldier a decade ago. A little girl's doll could be one, but only if it were a favorite- the fact of a toy belonging to a child does not make it "connected" except by their emotional attatchment.
On a physical level, a stone on the ground is not as attatched to a place as the same amount of stone chipped from a huge boulder- that is clearly far more [u]part[/u] of the place, more literally [u]connected[/u] to it, and how permanant that connection was. Look at the Examples at the top of 84- the shorter the duration, less "connected" that type of thing is. Be creative, then be confident- you're the SG, that's your job.
From 4th ed:
(useful, but remember- this was an "is/not" situation, and now, in 5th ed, less connected things simply fade faster.)
[b]Arcane Connections[/b][i]
Some spells, in accordance with the Law of Arcane Connections, require an arcane connection to cast. An arcane connection is some item that is intimate to the target of the spell. It might be an actual piece of the target, such as a stone from a cobbled street, clippings from a horse’s mane, or the hair of a person. Or, it might be some important supernatural piece of equipment, such as a magus’ talisman.
Exactly what is and what is not an arcane connection is up to storyguide interpretation in some cases. For example, a magus may be able to establish an arcane connection to a little girl through her doll, if she is exceptionally emotionally tied to it.[/i]