Yeah, been 'round that debate awhile, among my cutting buddies, some of whom are tree pros. There's good arguments to be made on both sides, and truly most of the pros just hand-sharpen every second tank fill, but they're also operating under different economics: sharpen on the clock, billable hours, versus spending personal time in the evenings.
I've always just carried one or two spare loops for each of the saws I'm running that day, so I can swap the chain out if I hit a buried antique electrical insulator or spike in a tree, both of which are too common around here. If I don't manage to hit anything, I'll still usually do a chain swap on the one or two saws I'm using most, when I take a lunch break mid-day. Hand filing might be just as quick, in those cases, but I've gotten awful good and comfortable with my bench-mounted chain grinder. It's always hard to deviate from that in which we've already invested time and energy in perfecting, in pursuit of something new, especially if it doesn't hold promise of any really enormous advantage.
