How can I maximize my stay in Thailand with a METV before its expiration date?

when this 30 days runs out, border bounce, get another 60 days, extend that if you want BUT make sure you bounce out and back in one final time just prior to the "enter before" or "valid until" date on the VISA itself. That gets you the final 60 day entry and you extend that by 30 days as well.

You can get almost 9 months of stay out of that 6 month METV if you get the visa as close to when you're comin' here as you can, AND you bounce at the right times to get another 60 days.