FWIW, I had a chance to inspect our Aspire pre-delivery. At the bath fuse panel, there was a fuse for the See-Level tank sender that had been pulled and taped to the panel frame apparently for later install at the dealership.
Same thing with the CO detector fuse, but located in the DS front equipment bay.
I would infer from this (but don't know for sure) that these two items are powered at all times and therefore represent a constant (although small) drain. Also don't know (yet) which battery they are drawing from.
Besides all the aforementioned other sources of parasitic drain, another likely but often overlooked, source are the inverter(s). The inverter is wired directly to the house batteries. Believe it or not it still can consume power even when it is "off". This is because some power is needed to keep the remote panel "alive" - just like your TV is never really off completely, it needs power to listen for commands from the remote. I have installed and upgraded many inverter systems for my marine customers and always include an on/off switch so it can be truly turned off during winter layup. I checked my Aspire and even when the coach battery is "off" the inverter remote panel remains live so it is likely this is part of the drain on your batteries.
I have found the pure sine wave inverters (like the Magnum on our newer Entegras) are bigger consumers of parasitic power than the Modified Sine Wave models. I don't know the exact numbers yet for the Magnum in my Aspire, but the Xantrex on my boat pulls 350mA when it is "off". Not much, but enough to run a 450AH battery bank down to 50% in just 25 days or so.
Since there is no switch in the main power feed on the inverter in our coaches, look for the Magnum ANL fuse near the back of the battery compartment (it has a plastic cover over it) and unbolt it during your layup periods. Be careful and use insulated tools, a short here could be explosive. If you want a more convenient method, add a rotary battery switch such as you can get in a marine store.
I also often recommend my marine customers install and learn how to use a tracking battery monitor. This will do a number of things but relative to this conversation it can tell you instantaneous amps in/out of your house battery bank. So you will be able to see if there is a drain, how much it is, and will be able to track it down without guessing. The down side of a battery monitor is that it also uses a small amount of power itself, but in the case of our Magnum inverters, we can simply add the ME-BMK
battery monitor kit and it will shut down too when the ANL fuse is disconnected as described above.
The ME-BMK kit will work with our existing Magnum remote display as long as it is rev 2.0 or higher (mine was v2.6 something). The BMK module just plugs into the network jack on the side of the inverter so all the wiring is done in the cargo bay. However, a "shunt" also needs to be installed in the negative battery loop which will involve at least one new length of appropriate sized battery cable. I am planning this addition and will post my installation notes when i have it completed.
If you don't want to install a ME-BMK get yourself a good clamp on DC meter. Not as accurate as a shunt, but when clamped over the battery cable can tell you if there is current flow, although very low values may be hard to determine. I have this one
but there are generic equivalents - beware of the cheap ones they are usually only for AC circuits only. A meter like this will probably set you back at least $75.