Sherpa still is talking about camping at Outpost before we (hopefully) summit and also after. I think it is because he (secretly without admitting it) wants to drop his load. Then get up early and hike 7 miles up, and down, without the pack. And camp a second night Outpost again. But if we feel good he may change his mind.
Another factor to consider is the terrain above Mirror Lake. The trail is more rugged up there, so it is more work to carry packs. I remember there was a post from some people who
Barely Made Trail Camp. Of course, many people who train well before the hike do not mind the extra distance.