Yep. Like djtho1 stated, the propane leak detector, your converter, and the sound system all draw a little power when you have the battery connected. Over a couple weeks, it can completely drain your battery, which will shorten its lifetime if you do that over and over.
However, the safest way to install the battery disconnect is to disconnect the ground wire, which produces little, to no arcing or sparking when you disconnect and gets you the same result - no drain on the battery. Minimizing the arcing/sparking is important, due to flammable/explosive fumes that could be present in the battery box and/or the propane tank cover, which will probably be in the vicinity of your disconnect switch.
just my safety-minded and experienced opinion.
2015 Jay Flight 32RLDS Elite
2012 Chevy 2500HD Crew Cab LTZ (6.6L Duramax/Allison)
Equalizer Hitch (1200# bars)