Great responses so far, everyone! Thank you for adhering to my request of being data-driven rather than superstition-based like the "oil is cheaper than engines!" repeated over and over again with no qualifications like you'd get on Facebook or Reddit (maybe 1% of those sites have people that...
Unfortunately for me, in nearly every case with my cars and bikes, the oil filter is the hard thing to get to. A couple of these could probably have the oil drained and filled without even lifting the car, but the filter is the hard thing to get to. I think I'm happy with a 3 year interval...
At this point, I have 7 total household vehicles (5 cars+2 motorcycles) and if you go by the bog standard maintenance book they would all need oil changes every 3-6 months regardless of miles (yeesh). As you can imagine, if I even tried to keep up with that, I would go insane. Only one of the...