I have a dimmer switch installed for the bathroom light at my cottage.
The light fixture itself has 6 small 25W lightbulbs. For the past three
years, the dimmer has worked perfectly. Three weeks ago the dimmer
stopped dimming and could only be used to switch on and off. I replaced
that dimmer with a similar (inexpensive) switch that worked quite well
for three weeks - then the same thing happened - the switch was blown
and would only turn off and on. This weekend I replaced the second
blown dimmer with a more expensive ($20) dimmer. It worked long enough
to show my wife how brilliant I was, and then stopped altogether. I
replaced it with a normal switch for now.

I suspect two things - a short in the light fixture or a short in the
wiring. On my next trip up to the cottage I plan to replace the light
fixture with a simple fixture and install a (cheaper) dimmer to see if
it the fixture that is causing the issue.

Any thoughts or advice on
1) what could cause the dimmer to fail after working fine for 3 years?
2) how will I be able to identify if there is a short in the light
fixture (ie what do I look for)?
3) how can I determine if there is a short in the wiring?

Thanks!