How I'm dealing with friendly NPCs in DFRPG Arden Vul

Arden Vul is full of NPCs, some of them in town, some of them in the Halls.  Some of those NPCs are actually adventurers who might be happy to visit the Halls.  Some are friendly to the PCs, and might be happy to accompany them.

But I'm not generally letting the PCs bring NPC companions into the Halls with them, for meta reasons.  My general rule is that I limit delves to 5 PCs, because each additional player or token slows everything down.  NPCs don't slow things down quite as much as PCs do, because they don't add additional players, just additional tokens.  But they still add significant overhead.  I tolerate this for key PC powers that they paid points for -- the GOAT's summoned animals are annoying to manage, but he's a druid and summoned animals are a major part of a druid's powers so if I allow druids I pretty much have to allow summoned animals.  But I'm not letting PCs buy the Ally advantage (which isn't in DFRPG, only GURPS, so it appears Kromm agrees with me), or pay hirelings to come into the dungeon with them.

So, basically, my rule is that if you rescue an NPC in the Halls, they may stick with the party until you get them back to town, and they may be your friend in town or even let you hire them in town to do non-dungeon jobs, but they're not coming back into the Halls with you.  Because I don't want to deal with a party of 15 dragging the game to a crawl, making it less fun for everyone, and eventually killing the campaign.  Of course like all rules there may be very specific exceptions -- if one particular NPC really wants to do one thing in the Halls, they may ask to come along for one targeted mission.  (As an example, Thalia, the ranger the PCs rescued in Session 21, really wanted to kill the vile 4-armed baboon Umsko.  But since Uvash already killed him, she no longer needs to go back to do that.)

Note that this kind of rule varies from campaign to campaign, and from game system to game system.  If I only had 2 players, I would let them each bring an Ally, and probably have them run each other's Allies.  If I were running a very lightweight system with no VTT maps, I could be freer with NPCs, as they would require less work to keep up with.  So I'm not saying that GMs who allow tag-along NPCs are wrong, just that it's something to carefully consider rather than blindly allow.