In theory this shouldn't be a problem. In practice I don't know. I took the GRE recently with double time accommodations and the process of registering was deeply frustrating to me. ETS lost my material on two occasions and made me jump through a bunch of hoops. The message I intend to impart is that you shouldn't count on ETS not being jerks about your accommodations. I don't mean to scare you but my experience has undermined any confidence I have in the organization being anything other than a hopeless bureaucracy (and I emphasize hopeless ). Plan your disability accommodations well in advance even if it's just the lesser half time accommodations.
There was an NYTimes article some time ago about how Congress was looking into ETS over various practices at the organization including, I believe, the disability accommodations process. You might go looking for that article, I didn't read it because I was extremely bitter at the time over their handling of my case and didn't want to hear anything more about the organization (stupid of me, I know). Finally another thing to keep in mind is that the peak season for taking the GRE is November through January. Thus, you will likely have more flexibility in scheduling if you don't do it during those months.