For a booking that is a long time in the future, you may not be able to keep an open pre-auth alive for that long. It might be wiser to do a small pre-auth at the time of the booking, to verify the card, and then do the pre-auth during business hours a day or two ahead of the actual booking. That way they can call the customer if there was a problem with the second pre-auth.
The pre-auth essentially locks funds in the customer’s credit card; I’d be annoyed if I had $200 reserved for a limo ride in 2 months locked for that long.