I've made BTN44 since then and now i'm able to gather 8 times from G5 spot with 138 Output. When i hit 50 i'll get all output gear I can have + materia for hatchet and it'll be clear how many attempts I can get on single spot.

It can come out, that 8 is a cap, but who knows I don't need +gathering gear anymore. Maybe I'll exchange some of Output for Perception.