As the script shows the last time each warning is seen, printing also the date when the must-gather was collected will help to know if the warnings are near the must-gather collection, or old ones (e.g.: if a must-gather was collected a week before it's checked, warnings 1 week old are relevant as they are the ones happening at the time the must-gather was collected).
For the date of the must-gather collection, there is usually a timestamp file in the must-gather directory. If that file is not present due to incomplete must-gather, maybe the date of the files can be checked instead.