In my experience a SS / IGH chainline is much less forgiving of a worn ("stretched") chain than a derailleur system, and even seems to wear them out faster. It's not that the chain will break (which can happen, but it's rare); but a worn chain develops a tendency to work its way off the teeth. The usual solution --to move the wheel back a little to tighten the chain up-- doesn't work for long. If you're not having any trouble, then you're fine; but be advised: sooner or later you will need a new chain.