Hi Ted!
When we have flown out of MHT, it hasn't been worth the $$$ to park and fly. Although I don't know the current rates for parking at MHT, several years ago it was only $6 a day. I usually get a room on Priceline (end up paying about $50 for the Fairfield Inn, I believe, I know it was a Marriott), call and make sure there are 2 beds, and we throw the air mattress into the van just in case!
Also, keep an eye on PWM for airfare. For most of this year, I have been finding as cheap or cheaper fares from PWM than from MHT, and you save several hours of driving time on either end of the trip. For our trip in TWO WEEKS, we are flying out of BGR at 6am and back to PWM, then taking Concord Trailways back to Bangor. This was cheaper than flying RT from PWM, and BGR prices were not to be considered!!! Of course, parking at PWM is now $13 a day (construction, everyone uses the garage) but that might be over by the time you travel. I know the Comfort Inn and the Best Western in S. Portland/Scarborough do park and fly at PWM.
Good luck... I'll keep my eyes open.
Lee