If this number is wrong, everything downstream is wrong, and no amount of routing cleverness will fix it.
Why it matters
A schedule is a sum of durations plus the driving between them. Ten minutes of optimism per stop across a twelve-stop day is two hours — the whole overtime problem, created at planning time and blamed on the technician at six in the evening.
Optimism is the normal failure mode, because estimates are usually set from the best case and never revisited.
How you notice it slipping
Every service type has a suspiciously round duration. Actual times cluster well above the estimate, consistently, for years. Technicians have privately adjusted by skipping steps, which is the version that eventually returns as a callback.
What to do
Compare estimated against actual time on site by service type each quarter, and move the estimate to where the work really is. Do it per type rather than as one company average, because a single generous number hides two problems at once: the service that is routinely over and the one that is comfortably under. A schedule built on honest durations finishes on time without anyone being asked to hurry, which is the only sustainable version of a full day.