We live full time in our TC. We have a large 11'3" Lance 900. Honestly, it's bigger than we need/want and want to go smaller! Even with the wife, our 45lb coonhound/aussie, and myself, we don't have big issues with space...but then, we all get along very well too!
I work full time, the wife is looking for work. During the winter, we leave the heater set to around 60 degrees with a vent open a small crack for airflow. When it gets warmer, we run the fantastic fan with a few windows open and it stays fairly okay. In the summer heat though, we will put the dog in doggie daycare.
I wouldn't say that our dog is super happy being in the TC 8 hours per day alone, but she's not bad about it either. We are very diligent in taking her for multi-mile hikes just about every day, so she get all the energy out.