I'm not quite sure if this response is going to be on target because I
may be mis-understanding you. I know from before when I didn't record
my dreams they seemed like they were over pretty quickly except on
occassion. Do you record your dreams? If not you may want to try it
out, I think that when you do this you will remember the dream better
as you're writing and realize how much time you spent dreaming. The
other thing could be that you are waking up near the begining of your
REM period which would mean that you indeed haven't been dreaming that
long. Since you mentioned work/college I take it that you are waking up
with an alarm. How many hours of sleep are you getting a night? If you
are only getting a few (like me :) ) then your REM periods won't be
that long. The longer you are sleeping the longer your REM periods are.
If you sleep for ~8 hrs I think your last REM period will be something
like 90 minutes if I'm not mistaken. There are other options that will
increase the time you spend in REM sleep. I think if you go to sleep
for ~6 hours then wake up for like 30 min - 1 hr then go back to bed
then you should have increased REM periods. These numbers may be off
but I'm hoping that I'm remembering them correctly. Most of this info
is contained in the book "Exploring the world of Lucid Dreaming"....if
you don't already have it you should check it out.