Once you get to Citadel 40, those packs will be replaced with Exalted Building Blueprints packs. If you want to be able to do fast upgrades after you hit Citadel 40, we HIGHLY recommend that you pick up enough Royal Building Blueprints to upgrade all your Main buildings and at least one of each RSS & Secondary Buildings to lvl 40 before you get to Citadel 40. And that's in addition to the 435 that the pack advertises and you end up totaling around 1,500 blueprints a pack. For example, in the pack below with 65 chests, in addition to high-level resources, such as Obsidian, you usually get an extra 900-1800 Royal Building Blueprints.
The Royal Building Blueprints chests in this pack are the key. It typically appears in your late Citadel 30s and disappears when you hit Cit 40. This is the pack you want if you just want blueprints. While you get some Royal Building Blueprints in most packs, it's usually only around 150 of them. First of all, make sure you get the 50% off of Royal Blueprints pack.
