Unfortunately, it is not. :/
Im really at TH6.
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Aww.. After going through 500 of your posts.. i do think you are legit TH6 lol. My apologies for wrongful accusations haha.
In that case.. If you are doing more than 10raids per day and your storages are always full then dont bother upgrading collectors above lvl 9.. You can do that in TH8/TH9 when all upgrades become expensive and whenever you don't have the gold to upgrade defences/elixir to upgrade troops/when your resources are empty and builders aare idle.
Am a TH9 and my collectors are still lvl 8 since i dont have the time to upgrade them yet.
Am not losing much from that since i do more than 5-10raids a day on average. But i think i will upgrade them now.
No harm in not upgrading them above lvl9 for a while.
As i said before Collectors are not needed for a good farmer. you just waste the builder time on collectors.
Mines are not needed until TH7. At TH7 IMO you should consider upgrading mines because after the new upgrade in TH8 it is hard to farm 128M gold for walls lvl8 in 80 days. (I calculate everything)
from Th4-Th7 I always could max walls before all builder-needs upgrade are done. but after entering TH8 I try hard to farm lvl8 gold-only walls. Now I have 30 skulls after 17 days. It is not bad but I should try harder to complete all skull walls in 80 - 17 = 63 days. my elixir storage is full now and BK will be lvl10 in 2 days so DE storage will be full soon. So I just need gold and every bit of gold is essential.
Anyway in short sentence mines are important to upgrade.