If you look at the domestic opening weekend box office for the two movies, you'll see how AEG blew TFA away. By more than $100 million!!
AEG: $357,115,007
TFA: $247,966,675
But, if you look at where both movies stood after just 17 days . . .
AEG: $723,745,643
TFA: $742,208,942
. . . you see how quickly TFA caught up to, and even passed, AEG. That's mostly because of repeat TFA viewings coinciding with the holidays. If TROS opens with a higher weekend total than TFA (it won't even need to sell as many tickets to do so), the same sort of holiday schedule will be in play again.
As TaliBane pointed out yesterday, nostalgia is a big part of the appeal for SW. And I think that nostalgia drives repeat viewings as much as anything. TLJ had little in the way of nostalgia, but TROS will likely be the complete opposite. Just look at the first TROS trailer: Lando, Palpatine, Death Star, and even a friggin' ceremonial medal from ANH!!
JJ will probably pack so much fan service into TROS that it'll seem like a SW retrospective feature.
If it has a huge first weekend, I think a $900 million domestic total could be possible if fans get a healthy serving of Member Berries.