There aren't that many electric motors installed in garages, except a CV system or maybe a freshwater booster. The one in the A/C air handler doesn't count, 'cause any ozone it produces is sent into the house.
I am not sure about this. A few weeks back the PowerSportsHonda Dealer in metuchen NJ told me that the cement flooring in the garage causes damage to the tires and advised me to keep the motorcycle either on some old rug or some rags. I am not sure if all Honda Dealers are on crack.
Ozone is created in the spark gap of electric motors (and welding, I believe). And, yes, it degrades tire rubber. I'd be surprised if running a central vac for 10 minutes a week would be enough, though.
Did you check the tire-manufacture date codes to see if the tires were built before 2005? If it was a 2003 tire put on a new bike in 2004, it might just be getting old.
Also, if the tires have been through a lot of heat cycles, that might contribute to premature cracking.
This reminds me of the old adage of how concrete floors could mysteriously suck the life out of a battery if you didn't put it on a slice of cardboard or wood. I never bought that one either, just a lame excuse for a cheapo product.
This is a well documented issue with central vac systems. They are notoriously jealous of motorcycles and have been known to sabotage them. The vacs are quite nefarious, but luckily ill equiped to do much damage. Somehow, they figued out how to prematurely crack tires though. Also, they'll put dino oil in your engine while you sleep.