If you use multi-grade the additives that make it "multi-grade" start to break down and oil consumption can start to go up because by design the engine has big clearances. The oil accumulates combustion by-product waste, lead, water, acid, etc. The longer you go the higher the concentration of that junk. Does it matter 25, 50? Several other variables need to be considered.
Multi or straight wt? (Multi additives breaking down, change oil more often)
Time interval between changes? Oil time, calendar time? (Whichever comes first)
Time interval between flying the engine? week, or weeks? (less frequent fly more frequent change)
Temp and humidity when storing and operating the engine? PHX or humid coastal area? (Dry air good, moist air not as good)
Temp the oil gets during cruise, too hot or too cold? (increase the change frequency as the temp diverges either way from approx 190 for continuous operation, If you drive around at low power looking at 150 deg or push hard and see 240+ all day, change it more)
Use an air/oil separator or inverted oil system? (Increase change interval, both those items return contaminants to the crankcase the engine had tried to expel)
There are more....