if a man hasnt had sex in months...

That's been my experiance.

That would seem to be the case, except, just because he hasn't had sex doesn't mean that he hasn't had an emission. Wet dreams or nocturnal emissions happen about every 14 days in most sexually mature males, when they don't have sex otherwise.

Your question assumes that he's had NO sex at all.

So, yes, it will take less stimulation to produce an ejaculation in a male who has a "full load" of semen or sperm stored in his seminal vessels. 8-| %-)