Do you guys think it's really worth it to spend the FP to get it beyond level 80?
Edited...
It depends on how far past 80 you go...
Past level 80 your Arc improves by 0.1% per level. This means that if you are giving a 1.9 contribution to another GB, for every level past 80 you will make 1 extra fp for every 1000 fp you donate.
If you consider level 80 to be the base, than...
At level 90, you make an additional 10 fp/1000 donated
At level 100, you make an additional 20fp/1000 donated
If you find yourself donating a lot, this can add up over time. However, it also takes a LOT of time. Going to level 100 isn't so bad. At the moment I make about 350fp per day. This means that it will take me 4 months to get from level 80 to level 100. However, after that, I can concentrate on raising other things while also making fp simply by doing things I already do now- donating to other arcs. I used to think the CF was the way to go, but after noticing this I switched up quick.
But be prepared. It's similar to raising the Arc to 80. You're probably not going to be doing much else of interest until you reach your goal. As I make 350/day I think level 100 is good enough until my fp collect improves significantly. At the current rate, going from level 100 to 110 requires
another 4 months.