[skrubol]

You might want to use threaded inserts (such as helicoil,) anywhere you plan on using threads frequently. The larger bearing surface of the threads, plus using some adhesive should help keeping the threads from getting worn out.
There are other sorts of threaded inserts specifically for plastic that are friction fit.

[robobass]

I might try that as time goes on, but I don't think there will be a need. An M6x1 gives me 12 threads. That's a lot. If does degrade, I can just bore out the threaded holes, make some round stock of the stuff on the lathe, and solvent bond it in!