Is it normal?

I main rengar, since starting playing this game, but if I'm not playing him a lot, it seems that I'm doing only decently. I have to play like 20-30 games to be able to play him as before. I don't want to seem cocky, but sometimes people call me "rengar god" kapa, even if I don't deserve, only becouse I don't miss my skillshots in some games ever. But after a while I start playing rengar even worse then before those 20-30 games. And then I quit rengar and start playing other champions.

Is this normal? Should I keep forcing myself to play him? I mean, I don't feed and get fed in almost every game, but I start missing like 90 % of my bolas even if target isn't moving and also starting to make bad decisions with him, when to engage, etc..

Some times happens very rare thing. I don't play him like for weeks, then I start playing him, I don't miss any bolas and I'm able to cary most of my games.