All though my only interest is the Napoleonic era, I do feel that the question is not one to be asked, as everyone has a main era but dabble in other eras, so in my honest opinion a fare spread of different eras being produced by manufacturers over the year would hopefully keep everyone happy and interested in the hobby witch has kept all off us so happy and frustrated over the years.
Happy collecting Phil

I only collect US themed conflicts. I agree with Robert, some of my units have been assembled for things like ACW. But I could buy something new if they are better than what I have or add to gaps.

Having said that, I find it puzzling that WWII US has many gaps. Everyone tries to shut me down by saying there are plenty of stuff already out there for US WWII (that argument never worked for WWII Germans or Nappy French, they still get made). But really, I wish HaT had made a heavy weapons set for the US like they did for the Brits. That would have been useful. And if Orion made US arty servants like the Russians, etc. I still can't assemble a decent US Marine force. I agree there are plenty of shooting and running riflemen out there. I probably don't need more, but I sure could use some radio men, arty servants, servants and ammo carriers for mortars and heavy MGs, stretcher bearers, etc. They would fill gaps and regardless how complete my army is, I need gap-fillers. But would that sell without the standard poses? Maybe not.