Earl BIS Dev: “The important part is to create the different LODs, not so much the higher poly count of the most detailed LOD.”
32768 vertices is a hard limit in ArmA – as direct x counts them. O2's points count is not quite the same thing depending on the number of sharp edges you have. I guess it applies to ArmA2 as well. I think its the max size of the vertex buffer. You'll know when you get there since buldozer fails to draw the model.
Models much over 20,000 points get to be very very sluggish in O2, of course models in that size should be modeled in other software and only imported into P3D through O2, or perhaps even use Synide's Modo plugin to go straight to p3d (but thats kind of offtopic).
Model that is more than 20-25,000 points is already very very detailed, imagine having few… dozen of these models appear in-game at the same time, talking about GPU stress. Anyways if you need the points then you need them, but it would be advisable to try to manage them down in any way you can.