It also highlights a strategy when using cards that introduce doom -- you can often mitigate the effect of their "doom" cost by playing them when you know that the threshold is already going to be met during the next Mythos phase. So, for example, if you have "Blood Pact" (which gives +3 to a number of tests at the cost of 1 doom), you'll be well served if you ensure that investigator has appropriate skill tests lined up for the turn before the agenda is going to advance.