Yeah, just keep an eye on the stuff to be honest.
You never know when something is going to brake until it brakes.
There are some obvious ways of finding out if something needs fixing, e.g. the freewheel is skipping; this is a usual problem with freewheels, but after a while you would want to get a new one.
To be honest, they are all different, I guess you just learn what to look for after bad experience of things braking =[