Our current rig came with 20# tanks. Even in cold weather, we typically get a month or more on a tank.
We do usually get them filled. By filling, you get 20# of propane instead of the swap places that typically give you 15# of propane in a 20# bottle. And the fill is typically cheaper than the swap.
The exception is when a tank ages out. Then we swap for a newer tank and go back to filling.
The supports might require some minor modifications but shouldn't be anything complicated or expensive.