zmx,
Welcome to the gym! Yes, unlike gym exercising, many men find that their gains are permanent. This isn't always the case, though. To keep the gains you make, you'll want to cement them (which involves weening yourself of PE).
About the time commitment: Many men see gains within the first week. Others don't see gains for months. To maximize your chance of gaining, you'll want to know as much as possible before you start. Check out our:
Good luck!