If you are staying at a Disney Resort, you can call to make ADR's 90 days from your check in date and make ADRs up to 10 days beyond that date.
So if you have a 10 day on site vacation planned, you can call at 90 days out and make ADRs for all the days of your stay.
If you are staying offsite, you can make ADRs 90 days out only, so if you have a 10 day offsite vacation, you have to call 90 days out from each date that you want to make an ADR.
CRT is the exception. It's 90 days whether on-site or off.