By the way, if your group always gets 10 chests and you don't have any magic buildings, then sure, go for the rrs, for now. But just because you don't have magic buildings now doesn't mean you won't get some in the spire. I've gotten 5 magic workshops in the past 6 months in the spire.
As a math exercise, I'll give you an example. My group averages 8-9 royal restorations per week and one blueprint. That leaves me with approximately 450 royal restorations per year and 52 blueprints. I have 7 magic workshops and around 15 magic residences. Since I turn over chapters around every 3 months, that means I need more blueprints than I get, around 88, so every one is precious to me and I need those only for magic buildings. I have a shortfall each year of 36 blueprints, which is a substantial shortfall.
On the other hand, I have something like 8 or 9 buildings that I really, really want to keep, basically from events and stuff that are really good that need to be upgraded. (Fire, aureate, storm, brown bear, polar, witch hut, and golem. I may want to put one more down.) The other buildings I have are very useful but not forever ... I can always replace them with better ones when there are events. So I don't need to waste rrs on the majority of the buildings.
Those 8-9 buildings total about 110 squares, approximately. That means if I turn over chapters every 3 months, I need no more RR's than I get in the year. So why waste blueprints making more, or using RRs on things that I'll only eventually replace anyway? Gosh, even the lava eggs, which I was CRAZY about, are not as good, per square, as the new building that we got yesterday in the event. I won 3 of those and teleported 2 of my lava eggs, which gave me more room and more goods.
I guess it depends on what you want, what your fellowship does, and how the math works out for you. For me, blueprints are basically only for magic buildings.