Specifically on MFC,
I have rarely had even a 4-digit tip. Tips over 500 elicit an "OMG I can't believe I just got that!" reaction from me. But I'm a fairly low camscore model on MFC.
Then again, since I'm almost never on... Well, it depends on what would give the user the most pleasure, but don't try to spread it out. Could take you a year to get it all to me, unless you were using offline tips. If offline tips are your thing, then yeah, please spread it out, a bit at a time.
Going by how I am now, I would say spend it all in the same day if you want to see my reaction, but not all as private time with no breaks. I start feeling awkward when a private goes longer than 30 minutes. Unless it's a lot of friendly chatter. Then afterwards I feel bad, because I feel like I was just paid to be a friend. Which maybe I shouldn't feel bad for, because I don't really have friends for very long. I'm not a social person, naturally.
Uh, rambling now...
Basically, I would want the guy to spend it in a way that would make him happy, without it making me upset, as a ridiculously long private/group would do.
CHANGE PARAMETERS
If I were on all the time, then I'd have a better answer. I'd want it a little at a time, in random increments. Random increments so that I never know when I'm getting it. Spread out over a long time, so that my camscore can feel the benefit for as long as possible. So maybe, wait three to five weeks between each spending. But spend in increments of 1,000 tokens at a time.
CHANGE PARAMETERS
Oh, you wanted the fun answer! In a world where I don't have to worry about either camscore or money, and can pretend that I can be on camera at the same time all the time....
Tip it all at once! I've never had that, and holy crap would it be exhilirating! I think my brain would explode trying to figure out what sort of show to do for that amount of money! (consider, my countdowns are usually 300 tokens at a time...)
OR, tip it in two 5,000 token increments! Never had that one before either!
But when you get right down to it, it's sad, but true. $500 only covers about a third of my expenses, so it's basically like saying "here, you don't have to worry for a week, take this week to experiment with shows that might not do well."