Will they get the stuff into your hold? Yes. Will they be efficient at it? No.For lasering LTDs, the collectors seem to do OK so far...
It will actually cost you time to run too many lasers for the number of limpets you have. The alternative when you have only six limpets for four lasers is to mine in bursts, but you might as well just go with two lasers. In essence, for your limpets to be "keeping up" with your lasers, the fragments should be targeted almost immediately upon being released from the rock. There should be essentially no down-time waiting for the collectors to tidy up after you have depleted the rock. If this does not happen, you are running too few limpets.
I don't know if you saw my video of laser mining in Borann some months back (note; the video is old - there is nothing but dust in Borann now):