I just happened to re-read the rules for investing powers in the Familiar bond, on p.105 of ArM5.
A maga may, at any time, invest powers in the familiar bond. This is a laboratory activity, and the rules are the same as those for investing a power in an invested device, with five exceptions.
First, ...
Second, ...
Third, the maga may invest any number of powers in a season, if they are all of the same Technique and Form and their levels add to less than or equal to half her Lab Total.
I am puzzled. How is this "third exception" and exception? It seems to me that's exactly what happens with "normal" invested devices too, under the Multiple Activities option on p.102:
All the activities you perform in a season must be of the same type (learning spells, instilling powers in an invested device, creating potions) and must use the same Technique and Form. To perform multiple activities, simply add up the levels of all activities performed and apply your Lab Total to the total of the levels...
... meaning that, even without the "exception", if the powers you want to invest in the bond are all of the same Technique and Form and your relevant Lab Total is twice the sum of their levels, you can complete them all in the same season. I have the nagging feeling I am missing something here. Any help?