How long would I be in the USMC DEP?

So I'm in th process of waiting for my green card so I can't sign with the Marines yet. I've talked to the recruiters and they said that I could PT with the crew from the DEP, now I've been going to the office to PT 3 times a week for the past 3 weeks and I'll keep doing it. So my question is by the time my GC arrives and I'm able to sign the contract for how long would I be in the DEP?? I'm wondering because I'm fit already and if I keep going to PT I'll end up in pretty good shape, and I see that the dudes that are in the DEP are just doing PT or not doing anything at all (except for that monthly meeting)... so yeah any ideas of for how long would I be in the DEP?