Originally posted by baldhermit:
Beldak: making it a skill challenge would kill the excitement of this encounter, so no, I would not suggest that.
What I am talking about is something I talk about (elsewhere) quite often, adjusting the encounter to the party. In this here case the party makes it into the fireworks factory by some means, they come face to face with dirty one liner guy, and at some point this NPC chooses to pull something out of his pocket, or perhaps already has it in his hands, and presses a button.
In every party I come across, there is at least one radar. You know the guy, "a pregnant brown haired mouse walked by that corner three weeks ago". Whatever his passive perception is, and perhaps the next PCs as well, he/they hear from the backroom the sound of a clock ticking, a sound that started immediately after the Puzzler pressed his button.
Players know what that means. There is no need to inform them of 5 rounds, as ideally you want them to feel like heroes, so you do want them to be able to free the Crackers.
So do not inform them of 5 round limit, forget yourself there is a 5 round limit. If the players ignore this sign and engage in combat instead of attempting to make it to the back room, make a show of the bad guys running from the scene, even provoking opportunity attacks while doing so, in a desperate attempt to get away. If your players are halfway smart, and they should be since they choose you to DM for them, they really should know what that means, and can make the appropriate judgement call (fight/flight).