Sorry if I get too specific, but here are some details as far as playing experience. I know nothing about the code that creates this experience.
With manual line changes and 10 minute periods, I like to alternate my scoring lines until they need rest - then checking line must be utilized. If the top line plays a minute then rests a minute while scoring line 2 plays, the top line is almost back to full energy again. This rotation doesn't balance perfectly (play vs. rest), so the checking line comes in when needed.
Basically, I like the way my genesis cartridge does fatigue, but I am ready to switch to a pi and use your historic ROMs.
Thanks!