Two separate occasions, actually. First: earlier this year I emailed Sprint's customer service to ask them to put my wife's upgrade on my account, and she said it would take two months to make the change. She wasn't kidding -- the upgrade didn't get switched to my line until two months later.
Second time: when we needed to use the upgrade for my wife anyway, and we went into the Sprint (corporate) store to figure out how to make that happen, the guy helping me said the exact same thing -- that it takes two months to make the change if you try to just swap the main-line 1-yr Premier Gold upgrade from one line to another.
Having said that, he did make it work -- probably by swapping phone numbers around, doing the upgrade, then swapping them back, which worked great and only took a few extra minutes. (Unfortunately, I think whatever he did meant I had to start paying the $10 premium data fee for my Samsung Moment as well as on my wife's upgraded line. That was the excuse I gave when I called that magic number and asked for our second upgrade early -- that there's no reason I should be paying the premium data fee on a freakin' Moment -- and he seemed to accept that as a valid reason, with no questions.)