Rushing back to the 'T' is critical and not something that I think you hear discussed that often. Most people are taught to get the back to the 'T' which is of course critical but with too much emphasis this can definitely lead to players rushing back to the 'T'. This can cause a couple of problems. Getting stuck and getting hit behind as well I would think is a risk too.
If you arrive back at the 'T' long before you opponent is going to play their shot it is very easy to get got caught flat-footed. If your opponent is very good at holding their shot as Peter Nicol noted Jonathon Power was then if you are at the 'T' too soon you have to wait, and wait for your opponent to hit the shot. They will definitely be trying to catch you flat-footed. Arriving back at the 'T' right when they actually are playing their shot will help prevent this from happening.
I think another point to this is that if you are to aggressive moving back to the 'T' you risk having your opponent hit the ball back to where you just left if they take the ball early. Your aggressive movement out of that corner will make it difficult to change direction and go back to where you came from.
Getting back to the 'T' is critical in squash but definitely take the great Peter Nicol's advice and try not to charge back to it. Move fluidly and try and arrive when your opponent is going to play their shot so you don't get stuck and caught flat-footed.