Here is a simple test you can do and get pretty close to how long it will take. 6-gallons is not alot of water.
Just get a 7-gal water container and go sit it under an open spigot and see how long it takes to fill up the 7-gallon container. This will give you an idea about how long it takes to recycle a standard 6-gallon water tank. It is up to the propane heater to keep the 6-gallon water tank producing hot water as fast as it is being emptied. With only the two us we do pretty good but sometimes we have to wait just alittle bit between the two times we both want to use the shower to allow the propane to heat the water back up.
They do make a 10-gallon hot water heater as well but the 6-gallon model is the most popular one used.
I'm happy enough to wash up from a sink but momabear needs to have her shower going...
just my thoughts
Roy Ken