The "batteries will discharge if left sitting on a concrete floor" is just an old wives tale. Think about it; the battery case is all plastic, which is a pretty good insulator. Plastics are used to insulate the romex wiring in your home which can safely carry 240 volts AC. I sit my batteries on my shop concrete floor all the time with never a discharge problem. If the battery is good and charged when you sit it on the concrete floor, it will still be good and charged in a month. (There is a small amount of internal loss for any battery that will affect the charge over time, but this is negligible for a month or 2.)
Just be sure the top of the battery is clean. Some discharge can occur through conductive dirt and crap that often builds up on top of batteries.
Propane tanks are fine left alone. Just be sure to close the valves...righty tightly...lefty loosey.
As for the stinky hose, I buy high quality hoses and use them to failure. I do inspect them at every use. Also, always carry a spare hose. Buy a second high quality hose, keep it in the package and stored under the bed or other out of the way place. When the "hose- in- use" fails, chunk it in the trash,... grab the new one, and then buy another, and store it. I cycle water hoses the same way.
My 2 c...
2016 Ford F-350 Lariat CC, 4x4 SRW. B&W turnover with extender. 2015 CC Silverback 29RE, fitted with Reese Goose Box. Amateur Extra Class K5TS, 2016 nights camped 16