@nativedeer depending on your current chapter it might take a lot of upgrades to get the buildings available in events now to produce sentient goods or mana. For example, I am (almost) in chapter 5. To upgrade a 3x4 building I receive now to produce mana in the Woodelves chapter, I would need 4x12 or 48 Royals Restorations. I'll probaby have many chances between now and when I'm in Woodelves to win buildings that will be just as good at producing mana without the use of Royal Restorations. (Or like mana hut be better with the use of the same or fewer RRs.)
Planning ahead is very useful in Elvenar, but sometimes it involves planning to wait. I did pick up a crevice just in case I want it later, but i probably won't place it.
Whether or not using RR's to pull good buildings across multiple chapters depends entirely on how fast or slow a player will proceed through the chapters...
Myself for example, I move at a glacial pace. Because I can stretch out my researches & provinces to camp out for a year+ in every chapter if I want to, I can amass a stockpile of RR's that will likely never be fully used up!
On the other hand, a player who speeds through chapters as fast as possible will obviously have to be extremely choosey with where they spend any RR's they have, thus, carrying event buildings from one chapter to the next is far less feasible.
A lot will also depend on if a player can get into an active 10-chest fellowship or not, as those who do, will earn 52 blueprints per year.
If you pace yourself at say 2-3 chapters per year, that should potentially still leave maybe 10-20 or so for crafting into an extra 100-200 RR's, depending on how many magic buildings really need to be upgraded per completed chapter. (ie: magic workshops can generally work just fine even if you leave them 1 chapter below your current chapter.)