Getting the nearly complete Library so early is a huge boon for you. I still need that one last piece for mine - and I have friends further along who still need multiple pieces.
Question - do you intend to spend the RRs to keep your ML updated? Either way, what's the reasoning behind your decision?
For sure I will spend RRs to keep it updated. I almost certainly would have done this even before the change to how AWs upgrade, just because the Moonstone Set is so good that it is not worth deleting the existing set to craft a new version. But after the change, it is a no-brainer. The Library itself has a cost of 12,000 SF and 25 CCs. It does pay for itself once you get the full set, but this takes nearly 4 weeks. Frags and CCs are so precious in my new city, I don't want to pay this cost more than once. Plus: if I deleted it in order to craft a higher chapter version, for every day I have to wait for it to show up again in the MA, I am losing out on its daily SF production.
Reason #2, I am already in a 10 chest fellowship and winning RRs and a blueprint weekly. And right now, the only buildings besides the Moonstone Set I regard as being worthy of RRs is my 2 Potionmaker's Pedastals. Which are only 3x3 in size. That is only 18 squares of space for both. Once I get the Moonstone Gate to complete the set, it will be 24 squares in size. This means that right now I only have 42 squares worth of buildings I judge worthy of RRs. That is nothing compared to my established chapter 21 cities, which have EXTENSIVE collections of both evolving buildings and set buildings from events. Those cities spend hundreds of RRs every chapter doing upgrades. In those cities, I spend a good amount of the blueprints and the diamonds I win from the spire making extra RRs in the magic academy in order to keep everything up to date.