Please give me some synonyms for priority (low priority, moderate priority, high priority etc.) relative to time.

Some examples which are relative to time:
Urgent | as in must be done soon
Critical | as in critical to be done soon
Nonurgent | as in not important to be done soon
Noncritical | as in not essential to be done soon

These examples are the most relevant I can find. I am particularly looking for low-priority synonyms; there seems to be less compared to high priority.