I occasionally buy a round for the crew but there is little doubt in my mind that when the F/A's ask me if I am coming down, they are usually just looking for someone to buy them drinks and nothing more so don't feel flattered when they ask. You are often just being used but if you want to think they want YOU to join them for your sparkling personality enjoy the deception. If I spend $25/night two nights a week on drinks or help pay for food that's $50 a week or over $2000 a year I would much rather put into my kid's college fund.