Once you start PE, you must never stop, because if you do, your penis will fall off. :)
If you slowly go from your routine down to nothing, then you should keep most of the gains. (But in life nothing is permanent, so if you do quit, you may lose some or even most over time.
I recommend trying to gain maybe 5% over your goal, then cementing those gains over a few months, that way hopefully you will end up with at least what you wanted.
Search for cementing, or keeping your gains, there is a whole lot here about this subject.
2007-01-27 5.3" BPEL 4.8" EG, Less than 3" Flaccid, and sometimes less than 2"
As of 12-07-2008 7.75" BPEL 7.1" NBPEL 5.7"MSEG 6"+ BSEG. Ultimate goal 8+ inches NBPEL, 8.5" BPEL 6.3" EG (2" diameter just sounds so cool!)
Flaccid 5+ inches on a good day. 4 1/2+ pretty much anytime. My gains have slowed to a snails pace, but I will not quit!!!!!!!