Since my battery monitor will show amperage drain, I went through all the electrical items on our trailer one by one so that I would know how many amps each pulled. Here's the list, which apart from a few items like the fridge and inverter, should apply to most Ollies:
All lights off, no fridge, no inverter - 1.2 A
All lights off, fridge running, no inverter - 3.7
All lights on, no fridge, no inverter - 5.7
All lights + fridge - 8.2
All lights + fridge and inverter - 10.2
Fridge - 2.5 (3.5 starting)
Inverter - 2.0
Reading lights, all - 0.3
Outside lights, each side - 0.7
Outside courtesy - 0.1
Inside courtesy - 0.1
Cabinet lights - 1.1
Main cabin overhead - 0.6
Right bed overhead - 0.3
Left - 0.3
Kitchen - 0.3
Dinette - 0.3
So I have 1.2 amps of parasitic drain. That's probably higher than most, since it includes my Cradlepoint router and Victron stuff. It's enough to kill my batteries in 12 ½ days, which I've verified. Solar is more than enough to keep on top of it of course, but if I were to cover the trailer or store it inside or in the shade, I'd want to disconnect the batteries.