I didn't mean to pick on you or your post, but there have been other people stating that 5E is easy because the group always goes into the dungeon, retreats to safety and then head back down the next day. That, or going into a rope trick for an hour or hiding in a hut for a long rest.I was keeping it simple for the purpose of brevity. Things are a'happening within context (for instance on the last excursion the group found that their exit was sealed off by the residents. I was simply alluding to the fact that there's no baked in plot-based ticking clock.
Time passage is a thing, naturally, as are the responses to player actions.
I'm just saying that in many cases you don't need a ticking clock, you just need the opposing forces react to the actions of the PCs. The PCs stopping after the enemy knows you're there (or should logically know) frequently will not be a good idea in my campaigns.