How long do I have to clean out a locker?

Most places say 24 hours. Some say 48 hours. If you build a relationship with a facility it can turn into a week !

If you think you might have trouble emptying it in 24hrs.....ask, before you bid, on time limits.

Most places I've been to have no problem giving 48hrs. 

You can also ask to rent it for a month.  Really depends on how many units they already have available and if its already been assigned a new owner.

I've even asked if I could I could rent it for a week.  They made me pay a month upfront but refunded unused portion.

Though I did stop in the office everyday, brought doughnuts, flirted with the....um......weight challenged manager.

Managers are for the most part very giving to those that are friendly and respectful.
Don't take their (or employee's) attitude on auction day as their normal personality.

If you don't get the stuff out within 48 hours what do they do about it?

If you don't get the stuff out within 48 hours what do they do about it?

It's up to the facility manager. Most will give you an extra day or two if you ask them for more time. Technically, they could resell the contents, assuming you signed a buyers contract and agreed to have the contents of the unit removed within a certain period of time.