The FAA had limited DPEs to two a day, and within a certain geographical area. That was stupid. They've fixed that in the new aviation bill (unless something has changed since OSH) so both of those limits will be removed. Heck, who wants to wait weeks to get a test date, and then run into weather? Doing four or five a day should be doable, if the DPE doesn't mind long days.
(As a point of reference, twenty-one years ago I paid $160 for the fee, about 1.5/1.8 ground/flight, and did it a couple of days after signoff. Limiting the DPE caused prices to rise, I'm sure.)