eBay rolls things out all the time, hundreds or even thousands of updates a week at all hours and times. Not just during their maintenance, so your assumption there is wrong to start with, thus the time length is also wrong.
Secondly, it takes Microsoft weeks or months to fix critical flaws 100x worse than this. Things that let hackers steal use of your computer, bank accounts, passwords, etc. And they're a billion dollar company. So in that respect even 12 hours is brilliant. This thread was started at 6:28am and my post of a fix was around 11:30am, about 5 hours. Another thread was started at 3am, so about 8.5 hours.
Also in eBays case rolling out a change means it can be hours or even days before it's on all their servers. So while it may be happening to customers it may not be happening to us when we test it because it's not on the servers yet that we're connecting to at eBay when we test. There have been many times where we've had to have 2 sets of code for things, one for eBays old servers, and one for the new, and we've got to figure out which is which on the fly and handle it with the right one. All of that takes time.