i dont go by months or miles.
living in subtropical southflorida, we dont have any cold weather, no wild tempature fluxuations either. so i change the oil whenever it gets tike. i get a "feeling" based on watching the oiul pressure guage and also the colour of the oil on the dipstick.
it isnt scientific or anything, but its what i do.
the shortest interval i have gone is 500 miles, the longest is about 6K miles, all on dino oil.
time has ranges from a week to over 2 years, again all on dino.
my father goes anywhere between 3K and 14K on dino. he also changes the oil like me, when its tikme and it feels right. things like rainy months, or if i do a lot of short trip driving which accelerates wear make me change it sooner.
i usualkly average about 3500 miles, however.