Simple maxscript command to replace a bunch of objects to one:
instanceReplace selection (pickObject prompt:"Pick instance source!")
It isn’t just simple replacer, but it make instances. So if scene contains thousand and thousands objects, differences in rendertime can be really huge.
The good thing is that it leaves original objects material, keyframes and scales. You can easily use it on post-baked particle meshes.
1.2 – Progressbar while replacing.
1.1 – Added button to select picked object.
1.0 – Better performance on huge objects count.
0.9 – Fixed possible errors on current selection catch.