Most Helpful Guy
Depends on what you mean by a good time? Are you constantly having sex? Is he mooching of you and getting everything he wants? Did he move in with you and not paying for anything? Are you always doing everything for him while he does nothing for you? If one or more of these questions match what's going on chances are he may just be there for the good time not the long run
Most Helpful Girl
If he talks about the future with a mention of you in it perhaps.
If he’s there for you to offer emotional support and not just there when there’s a chance he’ll get laid