if the windows were a custom size maybe their manufacture explains some
of the delay.
bonus your carpenter 10 percent for early completion before your
desired due date.
good contractors keep booked well in advance to keep their crews busy.
it recently took me a month and a half to get custom cut window blinds
delivered the "next day".
sometimes you're not leaving the store with that new tv until you buy
an extended warranty during the hour it seems to take to bring it
around to the front door for you.
if you find a good roofer or carpenter or plumber or hvac man or
painter or electrician, try to give him a full day's work and a good
tip. and more jobs.