How often do you change your tires? Mine are 25 and are again looking like shit - 3 or 4 large punctures on each tire and the’re only 3 months old. exactly the same thing happened with the last 23 tires - 2 months of great service then a series of punctures and end up looking pitted and scarred. Should I not be concerned about the holes and slits?
A guy in the local shop said they’re good for 20,000km, I am frankly dubious about this!
Sounds like you either have very bad tires or very bad riding habits or bad terrain or wrong tires for the terrain or… 
Pics/more specific info needed 
Lol, My bike is a working bike, I ride it for 1-3 hours EVERY day, every week.
The biggest crack/slits are not more than 2mm but they do go all the way to the inner tire.
Must be cheap/bad quality tires. Try a different shop or google for highly regarded tyres for your needs and try and get some of those when you ware out your current ones. I trust you keep them properly inflated. Must be bad quality. Which brand/tyres are they? It won’t be the width unless you are carrying too much weight. Be careful of debris where you cycle. See the tyre pressure thread.
Don’t worry about small cuts to the carcass, they’ll not be a concern to longevity…
You can close them with a dot of superglue if you’re really keen.
do worry about proper inflation and about cleaning your tires of debris after a ride and before the next one.
And more exensive tiR with a puncture resistant layer are worth their weight in bananas, or gold, or something.
Thanks. How many km do you change your tires?