I usually bash for a couple packs then put the cars in the basement. After a day or so, I'll charge the batteries and bring the cars up, then bash for a couple packs. After that, I'll put them in the basement again.
Next day or so I'll charge up the batteries and bash again, then put the cars in the basement.
They only get cleaned if they're so caked with mud or grass that I don't want them in the basement, and then cleaning is a combination of stiff brush (like the
Grunge Brush) and compressed air. If it takes 10 minutes that's 5 minutes too long.