Actually, there's something called hardware limitation and post-use depreciation, which means that no matter how well optimized you are, over time your phone will still get worse, not this, then the other.
What Hamid and everyone here have done, is probably all that's possible for optimization. so that's maybe the reason why he thinks it's time to stop.
Everyone, maybe, all has their a suitable preset. For me, I use current preset for 3 months, everything is good with it, then I almost have nothing to optimze.