I'm fairly sure it's still 32. I don't think it can be adjusted. This help doc also says 32.
They also say there is 32 on this site as well.
If you would like to be able to have more than 32 I'd recommend filing a feature request, I filed one quite awhile ago myself.
Not sure that 999 would be the correct idea, but more than 32 WOULD be good. Being able to adjust that in Preferences would be a plus.
In PS, the History States do require resources, but cannot comment on those in PrPro. Being able to adjust History States would be a good way to handle it.
There is no option to set Undo, its just 32 period.
Please file a feature request. If you find you need more then 32 undo's like many of us do.
As somebody who worked with Ps and many other apps that had ONE undo, I've become accustomed to saving at every meaningful set of changes, and using Revert to go back to that state.
And since Pr CS6 is so crash-prone, yea even at this stage of its evolution, I persist in saving at every meaningful stage of a project.
Besides, setting your Auto-Save frequency to a low value should cover you if 32 undos seems parsimonious.
I endorse the idea of a Feature Request if that's still unsatisfactory, although I have my own priorities (link below), and won't be joining you on this one.
As per your workflow, I also habitually use Save, and Save_As, plus a few Save_As_a_Copy, when a milestone has been reached.
Maybe it comes from Pinnacle, and then Avid Liquid, but my workflow is: perform operation, check it out, Ctrl+S, preview, Save_As. Perform an operation, rinse and repeat. End of day, Save_As_a_Copy.
Still, a more robust History State option would be good, too. As Jim Simon states, a few Nudges, and 32 History States gets eaten up quickly.