User blog comment:1onskates/MY CONCEPT OF BIOSHOCK INFINITE VLIGORS MUST READ!!!!!!!!!!!!!!/@comment-1853874-20100924200817/@comment-939754-20100924204153

Not exactly temporary. It just says they have a limited number of uses. They also mentioned that your weapons are more static. It forces the player to be strategic with what they have instead of like the other games, where if the player didn't find a weapon good, they could simply switch it out at a Gene Bank.

As such, you'd have to assume that, once you take a Vigor or Nostrum, it holds a almost permanent slot even though it loses its charges.

As a side note, Nostrums can also come as Unstable Nostrums, offering three different abilities. Once the player chooses one, it is permanently set to that ability.