I plan on attending ATP in early May with my private license completed. I currently have about 20 hours and I should be finished by mid-April. My question is, if ATP require 78 hours total time, would there be any benefit to coming in with even more hours? Or, would I need to repeat those hours anyways?
There is no benefit to coming in with more than 78 hours and there would not be any reduction in your costs associated with the program.
As for the 78 hours themselves, after you finish your PPL, call ATP admissions ans see if they will be able to sell you a time building package. This is not always available, but when it is, it is a good way of building time at a decent price and getting a jump-start on your instrument training.
Extra hours won’t help as far as ATP and your training goes, however hours are hours. They don’t expire and they’re yours and they will get you closer to the magic 1500 so if you want to fly then by all means.
The 78 hour minimum is required so that you will have the exact amount of required hours for the commercial check ride. It’s not necessary to arrive with more than 78, but extra flight time at your early stages is helpful.