I want to ask this question and ask for some legitimate positive replies. With each of the new events and improvements to the event buildings in stats, at what point are the vast majority of Great Buildings going to be obsolete? GE5 rolls out and everyone jumps to get the DC and SBC buildings to help them fight in GE5 but There are currently event buildings much smaller which can easily replace one of those GBs. A Deal Castle at level 89 gives 70% for att/def for city defense. 3 Monster Wares Boutiques can easily replace that one Great Building. So when a player gets so many event buildings which not only match but over come the stats for GBs where will our FP go? Sure if you are in Titan you can focus it on the 3 new buildings. But for a long time player who has stayed in Future Era and plays all the events and continues their city in that era what will they focus their FP after their Arc gets to 180 and say Observatory to 130? The new event building already gives 11 troops and almost every smaller building in the Halloween and Fall events have given troops... why build an Alcatraz? Are players just going to continue to bank the FP like they do coins to the point they have a Gazillion stored?
Will we see introductions of lower age newer GBs which require more FP? Will some of the GBs get updates like Observatory when GvG goes away?
I've already given up on lifting
% GB's. Keeping them around for aesthetic and nostalgic reasons. I've shifted my fp flow to other GB's that are offering a more secure beneficial buff. Things event buildings likely ain't getting: critical hit, Virgo, 1st strike, x2, etc.
It's more efficiently and economical to not using the
% GB's and instead using event buildings. Also for units it's more efficiently to use royal bathhouse for the moment. Instant excess to all current age units w/o the need for researching them first and no need to invest fps. Imho it's strategically more advantageous to focus on GB's that offer buffs event buildings probably never adopt: Virgo, kraken, CF, AO and Arc. Virgo for example at lvl45/46 offers around 60% + 5 daily charges. No need to lift it further. Virgo+kraken allows to beat GE5 with much less
%. Saving tons of goods on neg. and fortifications. While maintaining excess to 20%
and additional
%. For that reason it's quite useful and more valuable to me than any
% GB. The other GB's I've mentioned are no brainers. From those core GB's you could branch off to space carrier. For space ages to retroactively collect Mars ore. Assuming an age rush towards SAAB for more favourable battles. From there on it's possible to branch off to more luxury GB's like himaji, flying island, relic temple for extra fps and other rewards. Alternatively obs for guild goods efficiently.
In summery, besides a few GB's offering unique buffs, I think we've already past the point where levelling attack/defence GB's make much sense. The exception however is hydra. For its decent efficiency + guild goods. The other exception would be young cities with Zeus + LoA. To kickstart their A/D and working towards post scarcity of resources (goods/supplies).
While winter event is quite nerfed. A few of the best event buildings are available as dailies. So, I'll might be investing some free diamonds into those. Alongside trying to picking up the grand event building to replace an stages of ages. If it's all achievable this event could still end in an succes.
I found exactly one (in big letters ONE!) incident giving 20 stars (as logged by foe helper), might have missed one or other (due to not seeing, playing on mobile occasionally) .. wouldn't expect to have missed 6 to 8. 
