Elixir buffs are vanishing before 30 minutes timer expires. Most likely it happens when user leaves dungeons with the E > Leave option. There are other reports of the same problem in reddit, so it does not seems like a localized issue.
I think there is a mistake in the text of the descriptions actually. Elixirs seem to be on a 3 minute timer not a 30 minute timer.
Elixirs are definitely 30m
However they disappear if u log out.