Consistency with time

Q: What if my speaker mentions hours and minutes or days and months together? Do those count as the same category so I'd use numerals for all if one of the values is 10 or over?

A: Sure.

Since years, months, and days are all "measures" of time, we can apply the consistency rule (they're the same category) and use numerals for year and months since the days value needs to be a numeral.