When is it necessary to study chess?

Not very high to be honest. Some things like the Lucena position have to be studied. Just in rook/pawn endings there are many subtles that can't really be worked out at the board.

I know strong club players who studied a lot 30 years ago,have plateaued and live off the theory they took in then , but just play now...

I find enjoyment in studying and setting aside formal periods to do so. If you can't enjoy it, you shouldn't do it - I do admit though, the initial sit down for my designated endgame study period does take effort. We get out of the game what we put into it !

I'm going to assume chess is a hobby for you, so...

Play. If you have time for more than that, then study. From everything I've read here, becoming a Master is quite difficult.

You've been here for only days. Just keep playing. Improvement will be incremental as you recognize positions.

i think people who are tactically strong can do reasonably well, but once you play guys who can capitalize on weak positional moves, you'll prob get in trouble at that point - there is a lot to know, i have been studying pretty hard for like 2.5 years and i know i have just started - at the same time, i still lose and have nothing to show for my study at times - thats how it goess

sometimes the opposite happens and i feel like my chess work is all worth it haha

600. With some study, 850. 1200 players will mop up against players who never studied chess. Chess improvement is all about hard work doing serious studying over a long period of time. Fischer studied chess obsessively for over 7 years and was only in the 1700s.