Release packs love a single average. It fits on a slide. It rarely survives the afternoon when three large compile jobs land on the same agents.
What the average erases
An average build duration mixes queue wait, clean compiles, warm-cache hits, and the one branch that rebuilds half the world. If your cut decision happens on a Thursday afternoon, you need the distribution for Thursday afternoons—not the month’s mean.
A practical substitute
Keep the average if finance wants a headline. For the release checklist, add:
- Median duration for the last twenty builds on the release branch
- 90th percentile for the same window
- Share of builds that crossed your “too late to cut” threshold
Those three numbers still fit on one page of a ledger.
How we use this in audits
During a build & compile analytics audit, we ask for the raw samples before we accept any averaged slide. Teams that already track percentiles move faster; teams that only track means spend the first day reconstructing them.