Yes! Is a question opened to all. Of course the fast answer is "have common sense". Being conscious that Opensim is not Unity3D, with a graphic part absolutly based in polygons 3D (unless if you are creating these adictive games in 2D), I suppose that Opensim and the actual fan of viewers can't support a "super mesh party" too much time.
And, at this point: what can I do with my own work? Can I continue with mesh? Can I back to prims (I love, but I prefer use mesh because the results are most cohesive) like one year ago? Should I combine mesh with sculpts? In case of a negative answer, simply look at the Palace's stairs:
Then, I'm annoyed. But let me continue designing mesh, for me is a opened system and you can create something fastly with good results. For now we need the technical answer to know where are the mesh limitations. Or maybe you can not climb these decaffeinated stairs. Because, now, looking the screenshot...Is needed a little of colour.