Iit depends on how much experience and how many jobs you are trying to fit in the resume. 

I currently am highlighting just the last 17 years on my resume.  (That includes a 13 year position, almost two year position, and three temporary jobs.  This "dumb down" is due to my ' Baby Boomer'   age).  My resume is almost two pages long.  You really want it to be easy to read, so trying to cram a 10 or 15 year career on one page is next to impossible, unless you have only had one job in that time. I have  heard that most employers are only interested in seeing what you have been doing for the last 10 or so years, anyways.  You can always bring up your other previous positions at your interview.

I have never had anyone tell me it was too long.  Matter of fact, one man who interviewed me a few months ago suggested I put the job I had from 1984 until 1989 back on my resume.  Then, it would have meant 2 1/2 pages.  I didn' t, but do bring the job up in my interviews, because it was really the start of what I currently do (Full Charge Bookkeeping/Office Management).

So, you kind of have to think of what you are trying to accomplish in figuring out the length.  Don' t make it too short, and don' t make it so detailed the reader will lose interest.