"2 hours before Appointment time" seems to be the minimum acceptable 'standard'. Which I agree is really not very good.
Their reasoning is that there could be last-minute changes or even a cancellation and they REALLY don't want to pay us for printing docs that won't be used...hence, the 2 hr. thing.
If you need them sooner, I'd advise letting them know what your 'drop dead' time is ASAP and a brief reason (travel time is 1 1/2 hrs...is my usual reason)...be brief. Different companies have their own concept of 'when to send docs'; some will send them days before and some do the '2 hr' thing.
Even with the 'days before' companies, they do ask that you not print until '12 hours before' (to allow for changes, cancellations) and, even tho' you HAVE them, if you print 24 hrs. before and there ARE changes/cancellation 8 hours (sometimes less) before, you will have a hard time getting them to pay for the 'too early printing'.