After the panic of late 2012-early 2013, I stocked up, and bought lots of ammo whenever the prices were good. Still, I would not sell any, as the supply and price situations don't look like they will get better any time in the foreseeable future. While I have a lot, it's not an infinite supply, and I'm planning on making it last for at least the next several years.
BTW, Rob Ski at AKOU 47/74 astutely points out that having a lot of ammo on hand is for shooting at the range, not for SHTF. He says that if you get in that many gunfights, sooner or later you will encounter someone better than you. Sage advice.