Maxperson
Morkus from Orkus
I play my games with more realism than many. The world moves on without PC interaction, so NPCs will be engaging in this if it remains possible to engage in. Not many, but some would. I feel that it shouldn't be possible to swap out entire lists over the matter of days. If it was like 1 per month, it wouldn't be so bad, but it would also be next to useless for PCs at that point.In the most literal sense of theory? Yes.
In practice, I tend to make up an NPCs spell list on the fly, so I would never even be able to tell if they were switching their spell list every few weeks or not. Either they are enemies and dead, or they are allies and the players are likely only seeing them cast one or two spells anyways
Maybe if only one slot can be designated as swapable and forget the level limitation, it would give versatility without being too restrictive or allowing entire spell list swaps.