There a handful of wargaming must-haves...and some of them happen to be quite easy/cheap/small scale to assemble. Gladiators? Cake. Old West? Can be pretty easy. And with all of the Old West rules out there, it's always great to have the miniatures on hand. I think my only "knock" with Old West stuff is that the buildings and terrain are a bit specific so you won't get too much redundancy out of them.
Beyond that it's a great era to wargame. And if you get over your craze in a month or two...you didn't spend too much coin and you have some cool minis sitting on the shelf when the bug hits again in a few months or years. I think we all have those moments when someone suggests a game and you think "Wait, I have a bunch of old minis in a box somewhere..."