Glass!!

I've ridden on my Michelin tires for about 400 miles now, and I decided it was time for a tire exam.

I looked at every inch of tire surface and i found a few tiny slits. Two of them had something embedded in them. It was easy to get the first chunk out (GLASS!) but then there was another. I couldn't get it out with my hands so i got a pair of tweezers and pulled it out. it was about the size of this "o" a rather jagged piece of glass.
if i had continued riding on it, i am sure it would have eventually gotten to the tube.
That was an easy maintenance fix1

I need to inspect my tires also. Have 2025 miles on them. There are slits in places, and when I look them over I can't tell if there are things caught inside or not. I've tried looking out in the sunlight where the sun would reveal things, but didn't see anything. Have been a few places where I could see something in there, but it looked like part of the rubber of the tire.

So, questions:

How long before I should replace the tires?

How do I know whether a slit is truly clear or not?

A cycling friend told me of a trick he uses to keep the slits sealed on his bike. Says it gives him about 25% more use out of his tires. After inspecting his tires to make sure the slits are clear, he puts a little amount of super glue in them. Have any of you tried this?

well, that superglue that could be messy! I can see myself with my bike wheel stuck to the floor and me stuck to the wheel.
If you can't see anything in the slit, there's probably nothing there.

Those little slits don't make the tire wear out sooner. Only problem would be if another pebble or bit of glass landed in the exact same slit it might cut the tire threads easier. Personally, I wouldn't worry about tiny slits - only ones large enough to gap open when the tire is inflated. Buying tires with a thin kevlar belt is probably much more effective than superglue.

I had a mechanic and racer recently tell me he fills all the slits with rubber cement or shoe goo compound. Super glue doesn't fill any holes, it only bonds.

I only worry about slits and gaps in the tire if the core threads are affected. A boot will be fine on very small punctures to the core. Soft rubber compounds give good grip and traction but it comes at the cost of tires that wear faster.

I picked out some itty-bitty pebble wanna-be's out of the slits today. Strange to think something so small could pop the tire...