Every 15,000 miles for heavy duty service. Every 30,000 miles for normal service. Drain and refill only. Use a new sealing washer on the plug.
Dex/Merc ONLY. And even if you strip the plug, no worries. The plug is made to strip before the pan does!!!

 

One year I did buy a new drain plug with the crush washer.
But my concern was in what it takes to get the crush washer to "crush" to do it's job?
Use a torque wrench? Torque to spec? Going to have to look that up.
Go at it with a ratchet till flattens?
Good to know about drain plug cause that was one of the reasons I didn't use it.
Well that and not having a problem yet with reusing the old one.

 

Not much to worry about. It doesn't strip easily. You can probably find a torque spec somewhere. I've never used one and never stripped a bolt either.

 

15 ft-lbs on the drain plug. I rarely use a torque wrench on a drain plug or non-critical bolts myself. I just go moderately snug with a long ratchet. It's the pan screws you need to be careful on. It's real easy to deform the pan and cause a leak or worse,rip the aluminum threads out - lightly snug with a small ratchet is all you need.