Maybe if there are only like 3 of them in a total of 25 missions, then why not.
DLC's for Mafia 2 had all missions with timers that they were so annoying (they actually added timers, so people could compete and show off their best records, but as i'm not interested in competition, i just installed a patch that removes them).
Having timers all over missions makes you stop focusing on the fun of the game and keep rushing instead...