The website is actually called "Seeking Arrangements," lol.
That being said, when you say "long term arrangements," what do you mean? If you're talking about regulars, we've all got 'em. My favorite clients are my regulars, since we know what each other likes and what to expect.
I have had offers for a full-time gig, basically living with/nearby a client over an extended period of time. It's certainly an enticing fantasy, but, like someone else said, fresh meat is always just around the corner...