Sure. When placing a large number of objects I use the lasso tool, which automatically places the objects into their own group.
If I'm adding a much smaller group, say some objects close around a corner, Ill place the first one, then Split it from the default group (Split button), and rename the new group. Then, keep that group selected while you add the rest of the objects and they will be entered into that group. Keep checking and if some of them are not in the right group you can select them and split them off.
If you already have a lot of objects you can just select a bunch of them and split them into their own group.
It makes manipulation much easier because you can choose to hide the unselected groups and I would think that it also makes it a lot easier for the game to handle them too.
I do the same with large areas of textures too, but lasso selected a section and splitting that off from the main area and renaming it.
Hope that helps. Give me a shout if you need to know any more.
MVK