Nakamichi PA-7 Biasing Question

[Mercury3]

Hey sorry if this is a dumb question but wanted to ask.

I have two Nakamichi PA-7's which I use to drive a pair of subwoofers. (4 12 inch woofers (one woofer to each channel of PA-7))

I currently biased both PA-7's to spec at 40mv.

My question is since I use the amps for subwoofer use only would there be any advantage to a more conservative bias setting? Say 30mv instead of 40mv?

Would I notice any degrading in sound quality for subwoofer use only and also would that give me more peak power since I'd be running less in class A mode and more into class AB?

I'm thinking about since these amps are getting old a more conservative setting might prolong their life?

Or should I just leave well enough alone?

Advice appreciated, Mark