I have had a tank since i was about 16 - I can't imagine not having one. I have managed to do reef as a full-time student, and i can't imagine being any poorer than that, so I don't think lack of money will keep me out - as long as I live in this home, where my utilities are included... (not very green of me, but...)
I think there is WAY more good to this hobby than there could ever be bad, so I'm in forever, I hope. And when they have to put me in an old folks' home (a long time from now...) I'll bring my tank with me!!!!!!!
Right now I'm seeding my kids' desire to have tanks when they grow up!