There’s 2 keys to this job
1. Get the hell out of the depot ASAP
Sort in as little as possible and once all scannables are ready start delivering.
2. Memorize everything on your route. After a couple of months on a route you should know what’s inside each CMB so you don’t waste time numbering every scannable.
Do the above and you will always finish on time- with the exception of Christmas overload.
Of course, this doesn’t apply for relief- they should finish late and grab ot or ask for help.