Different tire pressures, different road surface adhesion's, whether you live in straight flat, or curvy hilly country, whether you spend a lot of time riding single or two up loaded, whether you spend a lot of time on the freeway at 80 mph or on 2 lane country back roads at 45-60 mph, aggressiveness of rider in both acceleration and braking, and even stature.... where you sit on the bike (EX: Being a munchkin, I sit on the front on the seat up against the tank, where someone taller sits back on the rear of the back seat maybe do to height or seat design, putting different weight bias on the front tire) ...all contribute to handling, tire wear, and tire life. All you can do is have a basic starting point and experiment from there for yourself. Most tire and motorcycle mfgs have recommendations, but they are just that, recommendations, not rock hard specific rules that you must follow when setting tire pressures.
2018 Yamaha FJR 1300A
2014 Honda CB1100 DLX
It doesn't matter what I ride, where I ride, or how far I ride... it only matters THAT I ride...every day. "Ferret"