I was really pulling for the leaf blower, but it let me down.
I don't think fluid changes have much to do with the condition of dust boots. Inner seals and piston, yes, definitely. You saw how clean mine were. I flush the fluid multiple times a year when I'm active at the track.
Heat and environmental conditions have a bigger impact on the dust boots. My brakes have been "well used" at track events where they are required to woah the car down from high speeds repeatedly all day long. I'm certain this is the reason they were in such bad shape.
It's a good idea to examine them well during brake jobs. I bet most people don't even look at them until they have a problem like a seized caliper.