Are the number of companions you own a cap on the number you can have in one thread, or a cap on your total?

In other words, would the following scenario be legal with only 2 mage companions, so long as I don't have all 3 companions in a thread at once?

Thread 1:
1st controlled NPC: Njall
2nd controlled NPC: Saya
Thread 2:
1st controlled NPC: Njall
2nd controlled NPC: Nami

It is a cap on your total. 

For instance, if you have 2 companions and you use them in a thread as "Njall" and "Saya," then those two companions would remain "Njall" and "Saya."  If you wanted to have a thread between "Njall" and "Nami," you would need to purchase a third companion to designate as Nami.

That's what I thought. Thank you for clarifying, though.

No problem!