As a general rule, if your cover letter is more than one page, it is
too long. Cover letters are supposed to be a summary (not an exhaustive
list as that is what a resume is for) of your work history, some of the
applicable skills you acquired on the previous jobs that will be useful
on the job you are applying for, an expression of strong interest in
the job being applied for, and a request for additional contact to
discuss the job you are applying for. Consider that the person reading
it will be reading your cover letter and resume along with, perhaps, 200
other people's resumes and cover letters. If they have to take too
long to review yours, they aren't going to be able to review everybody
else's in a timely manner. Try to keep your cover letter to one page as
an absolute maximum.
