This site has some excellent info on jack's and jack stands:

http://www.hyjacks.com/

The following page specifically addresses the question and is
titled, "Which Floor Jack Is Best For Me? Page". It talks about
getting approx 10 uses from a Chinese floor jack, which seems
realistic, since a friend of mine got exactly 9:

http://www.hyjacks.com/wichjac.htm

Other pages of interest -

Jack Basics:
http://www.hyjacks.com/H7.HTM

General Floor Jack History:
http://www.hyjacks.com/H2.HTM

Hope this helps....

Mark Hudgik
**91 Carat**