We currently have two brittneys, one 50 lbs, one 30. When we had our 30 ft 5er we had the two brittneys and also a beagle and there was more than enough room.
The beagle is now at the rainbow bridge and we have changed to a TC. Between the furballs, DW and myself, it gets rather cozy in the TC. We do have a slide and that helps.
We plan our trips accordingly starting in late spring to early fall to match our activities to the temperature. Our time away from the camper depends on the temperature. The hotter it is, the shorter the trips away from the TC when the furballs left behind.