My freewheel that I have installed myself only 1.5 years ago has totally worn out by the moment and so I just had it replaced along with a chain at the workshop. I'm still concerned though about the previous one's extremely short lifespan and thus suspicious about my current setup as well.
It's 7 gears freewheel on a folding bike (no front derailleur), and the problem is that it's feels very smooth on 4th gear. When you switch on higher gear up to the 7th, you start to feel some strange vibration as you pedal, which, I suppose, may indicate that the chain is not properly aligned and will wear the cogs out quickly.
Am I just being paranoid? Apart from that, everything seems fine now - gear switching is smooth and under load they don't switch lower with a distinctive noise, as before with my old freewheel. Should I try to play with cable's tension to get rid of that vibration on the higher gears as I use them more often than lower ones?