Not if you do it right!
I’ve made a few modules that make this very easy to implement. You would only clone things once!
My most recent handler module also lets you chose the FPS at which it would update object CFrames, so you could make the cubes move at only 30 FPS in the portal view. You could also make the map static, and therefore set the module to 0 FPS and massively save on performance since it’ll clone once and then never touch it.