Do you use Slime? My dad does and it gets gooped up in the valve and we have to take the gaskets out of the valve and clean them with a toothbrush. PITA!
This is off-topic but kind of funny...
When I started biking I had a lot of flats. Turned out my tires were so old the rubber was brittle and it was poking holes in the tubes. I got armadillo tires with kevlar and I was super impressed with a) kevlar and b) the armadillo concept.
My dad got his bike out and decided Slime was the thing. I didn't jump on the bandwagon because after the new tires I've hardly had any flats since.
He and mom were house-sitting for us and he brought his bike. He had it in the kitchen and was airing up the tires when the tire exploded. Slime ALL OVER the kitchen. He cleaned most of it up before we got home but I still found some green spots...on the ceiling.
Then I had to help him clean out those valves and that "sealed" it, ha ha. I told him I hadn't been fond of slime after he slimed my kitchen and now that I'd cleaned out those valves I'm totally against it!
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike