I have a vague memory that if you move out of state, and do all the proper notifications (certified letters, etc.), they expire your license on the spot rather than canceling or revoking it. So that if you should ever happen into the Commonwealth with firearms and ammunition again, the same provisions about "possession/carrying on an expired license" apply.
Is that true?
Of course, the right thing to do is to get a nonresident LTC, especially if you intend to visit MA with firearms and ammo. But if the "expired license" thing is true, at least it saves you from being an unwitting felon if you cross the border by accident.
Nonresident LTC is its own pain because it's $100, requires a trip to Chelsea, and is only good for a year. :-/ There's a bill pending to change that so it's valid for 6 years, but who knows if that'll pass.