Truck is every 1000 miles or so, usually down about 1/2 qt by that time. Top it off and check in another 1000.
Wife's Santa Fe, Was checking every fill up for the first year we had it, never down any, so now only about 1/2 way through the OCI (~2,500 miles).
Scion is checked every few fill ups. Never needed topping off, but has been about 1/2 qt low at time of oil change.
Mom's Kia, whenever I see her, every few weeks usually. Has never been low in the past year.
Motorcycle, only just before and just after changing the oil. In the 2500 mile OCI it has never gone down, so not worried about it.
Sisters vehicles, when I get a chance, usually every 2 months or so, usually adding a qt to both of them.