When I was younger, I'd do each individually, with the occasional repeat camo scheme. Sometimes I'd get a little froggy and do a whole lance at a clip. Since coming back from my hiatus of a decade, I'm a little more ambitious, and I've actually started doing the same scheme across many mechs, and searching out parade colors from some of my favorite units. I've got the makings of a battalion of Fifth Sword of Light built around Sorenson's Sabres, both the original unit from the scenario pack and the new one from Sword and Dragon. I'm also doing up a unit of Davion Mechs (only a company so far, but I wasn't planning on doing more than that for the SoL initially) in 7th Crucis Lancers parade schemes.
I've also found myself stripping some of the older models in my collection, some cause I painted them fugly, some cause I want to build a couple units that have more unseens than I've got without paint (like the Black Widow Company). I'd like to think I'll stop at a battalion for some of these, but I have some fear I won't. #P