FETs seem to fail quite regularly ...

[vikoma]

Trying some LED brightness control circuitry (for LDR volume control), I found that many pieces of 2N7000 have failed. At least 5-10; all during usual experimentation. And one of them within the circuit - it failed (i.e. shorted between G and S) when it was seen to be working earlier.

Since we use SK170 in Pass B1 etc., do we have to be careful? Of course, no one has ever reported a failed component in the Pass B1 designs. Any best practices there?

Usual reason is that it is due to ESD, which I suspect is NOT the reason in our country. The comments in thread below have more potential reasons; one of them being formation of oscillator due to capacitance inherent in GS junction of an FET.

The shocking truth about FETs | EDN

 

[sachu888]

FETs and opamps are quite rigid. They seldom fail unless there is a major issue. I have seen people soldered then reversed by mistake on B1 and still got it worked.
They might even blow in normal condition in case of fake JFETs.

Regards
Sachin