Sequence of electric and gas operation in water heater

I use the electric all the time and when I shower I flip on the gas as well. It helps to keep the water hot longer.

I am really surprised in the hot time difference between a 10 gl. attwood and a 10 gl.suburban. The atwood when supplemented with the gas heat never ran out of hot water with 2 people showering consecutively. With this rv the suburban runs out of hot within the first shower.