A tip to making "Life-long clients": BE EXCEPTIONAL. A client's concerns always take precedence over our own. Always put your clients first. Go ahead, be exceptional.
It's that simple. You know, it feels greater-than-great seeing a client's face light up immediately following a closing. I'll never get tired of it. But you can also get your clients to give you a similar full smile when you show them that you are there to help them...ALWAYS. The transaction concludes, and you all know how to stay in touch (I hope! ) But it's more than just that. Treat them like you did when you were selling / buying their home. Serve them well and entirely. Sincerely. Always be exceptional.
Don't even approach each client or practicing real estate with this mindset. (As a side note, isn't this going to put you leagues ahead of 99.9% of your competition? Referrals anyone?)
Always think, "What else can I do for Mr. / Ms. __________?" Follow the routine, give more... and first, always, and due payment will soon follow. (And I'm not even thinking monetarily, actually) Be exceptional in 2008! Cheers!