Welcome, Dragoon.
You're tackling this problem from the right angle - kudos for thinking ahead.

Exporting the 4 building types as separate DAE files and then only having to re-import the model that has changed (by isolating the model in a
3D View in Revit prior to exporting it again) is indeed the recommended way for scenes that take a long time to export.
If it takes ages to export the whole scene in Revit, you're right to be concerned about the model complexity as a whole, and it's crucial to nip this in the bud before you start populating your scene in Lumion. I suggest we carry out a feasibility study before we tackle the placement of the 4 house types first, as we need to figure out how much you can optimise the models and how your PC will cope with the 60 houses):
1) My recommendation would be to start thinking about the camera angles you'll need, and based on that, you should hide smaller details and other (unseen) parts of the buildings in the
3D Views you're going to export from Revit. Round surfaces are particularly important to hide as they are the most detailed surfaces. For example, if you've got a fully modelled bathroom but you aren't planning on rendering this room type, you should hide all the models in that room in your "optimised"
3D View before exporting the model.
2) In addition, you'll need to experiment with the
Surface Smoothing slider in the export options in Revit. This slider determines how complex rounded surfaces such as tubes and cylinders will be during export. The goal is to set the slider to the lowest possible value that you can get away with (whilst ensuring that there aren't any obvious "blocky" eyesores in full view of the camera angles you've planned in step 1).
3) Once you're done with step 1 and 2, import each of the 4 houses as separate (.DAE file) buildings in Lumion, and then place the 15 duplicates of each house, so that the 60-odd houses are visible on the screen at the same time. The real-world positions are not important at this stage.
4) Then press the F4 key to select 4-star quality (the best preview quality option in
Build mode).
Move the mouse cursor to the small white square in the top right corner, and let us know what the
3D Point number and
FPS number are.
5) Please also attach a screenshot of your benchmark results screen (click on the bar that shows the overall benchmark result to access the more detailed benchmark screen).
Once we've got this information, we can start to look at how to place the 4 house types in eir real-world positions with less effort in Lumion.
6) By the way, which version of Lumion are you using?
The limited 7-day
Lumion 7.5 Trial version (available on the 'Try' page) or the fully functional 7-day
Lumion 7.5 Pro Trial version (available via your local reseller)?
The reason I ask is that if you're using the former, I should mention that scenes made in the limited 7-day
Lumion 7.5 Trial version cannot be opened in other versions of Lumion (this is by design). Scenes made in the fully functional 7-day
Lumion 7.5 Pro Trial version are not affected by this limitation.
I'm just bringing it up in case you end up purchasing a license after evaluating Lumion as I wouldn't want you to lose any sleep over lost work so to speak.
Hope that makes sense.
