There are a couple weddings DH and I attended that did this, one had it at their hotel after the wedding, the wedding ended early though, maybe 3PM and the party was at 10 so everyone had time to relax in between. This couple had TONS of OOT ppl they hadn''t seen in forever, so they really wanted more time to hangout w/their friends. They partied all night until their HM flight the next morning (crazy!!) They had all the leftover cake there, and bought a bunch of chinese takeout. They had a suite at the hotel, cleared out a lot of the furniture, had a friend DJ, and it was lots of fun.
Another couple also had a lot of OOT folks, and we all met up at a local bar after the wedding... it ended maybe 9PM and we met up around 11 or midnight to give ppl time to change and stuff... but anyhoo they were a big party crowd and they drank wayyyy into the night.
DH and I didn''t do this. I kinda wanted to, but DH really wanted to have some alone time, and we decided that if we were going to do it, it would be last minute spontaneousness... and I''m so glad he convinced me not to plan anything, bc I was dead on exhausted by the end of the night... our reception ended at 10, and although i think I woulda been fine if we had partied another hour, I was pretty much done by the time we got to the hotel... it was sooooo nice to just soak in the hot tub and relax.