Here's how I'd modify your macro to do what you want without pausing for 15 hours (new/modified actions in yellow):
alarm macro 1.1.kmmacros (3.7 KB)
The trick with this is that it uses a companion macro that uses a periodic trigger a la @DanThomas's suggestion above that starts checking the SleepTime
variable in the evening and notifies you once it's passed 15 hours from the point that you set it:
Sleep Time.kmmacros (2.6 KB)
EDIT: Revised macros to enable and disable the Sleep Time macro so that it doesn't keep spamming notifications after the initial one. Of course, if you want to be reminded periodically until you go to sleep, you can always disable those actions and/or disable the Sleep Time macro manually.