First I'm sorry you are going through this. Second it is a great learning opportunity! How old are you & your bf? Did he not get the partying out of his system when he was younger, is it immaturity for a young age or is he trying to re-live those years? Do you have children or a child, it didn't appear to be so. You've had a long relationship, I think communication is ALWAYS key to any success in any avenue in life. You need to ask him what is his long term goal? How does this new life style fit in? Would he be amicable to cutting back or including you, are you even interested in this type of life style? A lot of ?s only he can answer, but better now then after your married or having children & your left alone to raise or with a drunk or partier who needs his priorities straightened out.
Be brave & courageous. Have that conversation that makes you both feel empowered to take your own way in life. Either he will man up or party down, but please don't settle or let it go to far. Address the issue, voice your concerns & make a firm decision. Not coming home, taking unplanned trips etc is immature behavior, which you are TOTALLY justified in stated that behavior for any man in a committed relationship, is not acceptable and should not be tolerated.
Good luck, this will make you a better woman & him a better man!