Recovery and Sabbath duration

How well would the Sabbath duration of Holy Magic work for recovery spells.
Because spells with this duration work for a full week except on Sundays I wonder how a they would work for wound or disease recovery if the spell is refreshed each Monday.

I would say that it's not good for recovery. It ends on Dawn of the Sabbath, and can't be recast until the next day. So there will be more than half a day each week that the target will not be under the effect of the spell. Say, it goes from dawn until midnight (assuming you cast the next spell at midnight the day after the sabbath). That's from approx 6 am to midnight, or about 18 hours a week. (YMMV depending upon latitude and time of year.) That comes to about 10% of the week that you're not covered by the spell. Purification of the Festering Wounds clearly states that for bonuses to Recovery, the target has to be "under the influence of this spell for the whole of the recovery period."

Now I'd give a little wiggle room on that requirement. But having a full 10% of the time not covered seems a bit too much for me.

Clearly the 40 Duration is much better, since that will clearly last the whole Recovery period. I know that's +1 magnitude, which means -3 to the Recovery roll. But I think you have to suck it up and take the lower Recovery roll.

After reading ArM 5 180 "Healing Spells" again it became clear spells that give Recovery bonus need to cover the full recovery period what means the Sabbath duration can't work here.
So Sun duration could work with a lot of work for the magus as it need to cast 2x a day but Sabbath not because the spell don't work for one day each week.

We would allow a patch for a sun or two spell to be cast in the Sabbath to cover that time... And would forgive a flicker. But it would need to be well timed.

I think you have to forgive a little flicker, or more likely add a little give into the requirement for "total' coverage, or the whole Recovery-boosting spell concept falls down.

The basic spell is Moon duration, which doesn't cover the whole season either. You'll have to recast that spell when the moon rise/sets, and there might be some lost time there. As I said, I'm willing to accept some lost time, just not most of a day every week.