Matt, when you left and came back did you get a new (different) Sensation phone or is this your original phone (reactivated?) that is now having this problem?
Its a new one. I had previously sold my old one. It charges the phone at 100% but I have to restart it. Charge at 11pm with a 5% battery and then at 6am it still charging. Then I restart the phone and its fully charged and fine. My battery lasts the whole day. I have written to HTC and haven't heard anything from them yet. I do plan on pulling the battery out and perhaps doing a factory reset if the problem continues.
This Sensation seems very solid where as my first one was very creaky. Looks like the Sensation for T-Mobile does have a lot of issues. I have also read that the myTouch 4G suffered from this as well. It could be software related, I don't know. I will definitely be calling HTC on the phone if it continues.
Can't exchange it at the T-Mobile store because I already exchanged it and they clearly say you get 1 exchange which is BS. They also increased the restocking fee to $50.