Is this sentence correct?
He does not come as often as he used to.
You will hear that, and you will hear it without "to". I don't know if "He does not come as often as he used" stems from the days when it was frowned upon to end a sentence with a preposition, but logically "He
used to come more often" would convert to "...than he used to".
I think you'll hear the version you posted more often.