Optinmonster has thousands of monthly paid users because they have one of the best countdown timers in the industry which can be created in top bar, popups (each type has dozens of different pre-made designs you can choose from).
Please offer 2 versions:
Static: Set a universal deadline for all visitors. You select the date and time the countdown ends.
Dynamic: Create “evergreen” countdown timers customized for each visitor. Instead of selecting an end date, you choose the length of the timer in days, hours, minutes, and seconds.

Is this on the roadmap and something that will be added soon? if so will buy immediately.