We've been full timing a 2003 Trail Lite 5th wheel for about 3 months now. The holding tank lights kinda come and go as far as working. FWIW.... you can look down the toilet and see when the black water holding tank is full and tell when the gray water tank is full when it back up in the shower. That said, we kinda know when they reach capacity. We dump out about every 3-4 days.
Judging by you picture, you might want to think about painting your roof. At the very least, give it a good cleaning and inspection. We cleaned and painted our roof with Henry Tropi-cool 887HS, as we live in Florida.
We've only been in it a little over three months and have already put about 1800 miles on it. Loving it so far, hope you do too!