I do my preventative maintenance based on time as well. Oil changes and whatever is on the check lists from the owner's manual every spring and fall. I do record the mileage when I write down the date when it was done but I rarely bother to calculate how many miles that has been. Every April and October.
Just out of curiosity, I just checked. Last April was 3,969 miles and October 5,044 miles for the 2011 and 5,906 miles on the 2019 in November since I bought in June. Some of that has been drives across the State for SAR training and the girlfriend taking the 2019 to Florida to visit her sister while I was deployed. So, a bit early on the mileage side but it gives me a chance to look everything over real well after the winter brine bath and before the winter brine bath.