First of all, thank you for your feedback!
The delay for getting colder is intentional, to give a meaning to the jam's limitation. To get colder, you have to press and wait, while to get hotter you can just smash it. The idea was that the player has to remain calm and just press it once to avoid detection, instead of just smashing the button!
Getting to max heat and outrun everything is a valid tactic, it's more "luck based" than sneaking around (especially in the last level with lots of enemies), I think both are fun in their own way!