valve clearance question (again!)

[limax2]

My mechanical mate says to just leave it until I hear valves rattle. 

That's all very well if the clearance is increasing but, as others have said, it is more likely to get smaller. The first you would know would be when an exhaust valve burns out and one cylinder goes on strike. That said most when checked at 25000 to 30000 miles (40,000 to 48,000 Km) are still within the limits, but not always.  Armed with your manual, a set of feeler gauges and a few basic tools it's a nice little job. Go for it  . Mind you, if they need adjusting that's somewhat more involved.
All this has promted me to check mine, so that maybe answers your question "what do you peaple do".
If the cam chain rattle is not too bad it could just be that the tensioner is getting ready to move onto the next notch. When that happens it should go quite again. If it gets bad I would investigate as a broken cam chain is bad news.

If carb balance is the cause of some rough running I would sort it. Why put up with it till it gets really rough  . But then I do have a set of gauges for the job.