The traffic (the number of items) for your office is recorded each day.
Your manager will have a fair idea how many items your walk gets.
He therefore has a fair idea how long it will take to prep that duty.
Assuming you are still on a 3hr 30 delivery you have about 1 hr 30 indoor time.
If the duty had about 1500 items/day I think your D2D should be prepped for you.
If you have less mail you begin to have time to prep your D2D (assuming you don't have masses of redirections)
The time allocated for prepping D2D relates to the number of delivery points.
If you had 3 contracts and 500 delivery points it "should" take you about 10 minutes to prep the 16% D2D each day.
If you had 3 contracts and 1000 delivery points it would take 20 minutes each day.
The busier the walk is the less time you have to prep the D2D.
The more D2D contracts you have and the more delivery points you have, the longer they take to prep.
So if you had masses of mail and loads of redirections and lots of D2D contracts the longer it would all take.
This means you might require assistance to complete your delivery within your contracted hours.
Part of that assistance might be help with your D2D prep.
Some might call it a loafer's charter.
I call it a realistic workload.
The societies of consumption and squandering of material resources are incompatible with the idea of economic growth and a clean planet.