Going from my response in the D/T thread...
This is how I see the band now...
The band has found a style that they all gel in, and they feel like staying in and exploring it, rather than dipping their toes in it, getting a taste of it's warm and relaxing and even therapeutic quality, and then getting pulled out and moving on to the next one. And I feel they did that with their Self-Titled album. That is the album that truly defined the present day Dream Theater sound and style.
They were forced to leave their current hot springs, as it decided to ease the overload of the crowd, and chose them to leave the spring (MP's departure). So the band, found a new hot spring (Mangini), and dipped their toes in it (ADTOE), basked in it (DT), and now quite enjoy it (D/T). The decision they enjoy the spring is after JP decided to make something to eat, and the band stepped out to make some BBQ (The Astonishing) before going back into the Hot Spring....
Which is where we are with DT15. And it is looking like they are really benefitting from basking in this Hot Spring.