My previous 20lb'er lasted over a year and was pretty heavily used.
My brother, on the other hand went through a 20lb'er every 4 months or so, and that was strickly serving single kegs at a time...probably 8 kegs or so. He also had a leak.
In case some aren't aware (and neither was I until recently), the thin white teflon tape primarily used for water or liquids, and there is a thicker tape that is used for CO2. It's usually colored red, yellow, etc. It makes a much better seal for gas.
I'm using a liquid thread sealant on all my gas threads now and it works great too. Princess Auto for about 5 bucks. The container is a pretty good size and has a little application brush fastened to the lid.
