Through the end of March, you can earn double AA miles for all stays at any Hilton property. I’m more of a Hyatt (and to a less degree Starwood) guy. But, if you happen to have some upcoming Hilton stays, there’s certainly no reason NOT to register.
And, as Gary from View From the Wing often recommends, you’re better to register for all such promos when they come out just in case you have an unintended stay later. No sense in missing out on points!