"average time from" is correct and usable in written English.
For example, you could write: "The average time from London to New York is 8 hours."
The average time from exposure to illness is 30 days.
According to Google, its average time from "Search" to find is 0.29 seconds.
The average time from presentation of symptoms to diagnosis is 13 years.
Average time from curb to gate is 20 minutes for the US Airways Shuttle".
"The average time from complaint to respiratory arrest was very short," she told the court.
The average time from nomination to confirmation for a Clinton district judge was about three months.
Results: The average time from surgery to MRI was 28 weeks (range, 4 to 54 weeks).
The average time from skin incision to closure was 4 minutes and 19 ± 33.6 seconds.
The average time from when the idea is agreed upon, to putting on the exhibition is probably about two years.
Parking is $6, and the average time from the curb out front to the gate is a half-hour.
The average time from reporting an offence involving a child to a crown court trial is 13 months.
