I fully agree with lhkbob.
I'm thinking about joining a cluster of decorative trees in one model, let's say 5 trees in one obj model, and render it instead of rendering 5 trees.
Do this in your engine. You can combine the geometry at runtime, purely based on model properties (does it share a texture?) and information like instance locality (combine all geometry in each cell of a grid).
Yeah, I thought about that, it would be stupid to spend more memory and disk space in storing/loading another obj with data I already have ready to use .
Thank you both for the info .