[Closed] Approx how many miles do you get out of a front tyre?

If you're talking about tyre wear, is it basically all about the tread?

Reason I ask is that I have a nobby nic on the front that is over a year old, but the nobs look in very good shape. I've fallen on my aris once or twice recently, and have been thinking of replacing the NN. Riding conditions are bad, though, so I couldn't for sure point to the front tyre as a problem. Does the rubber just lose grip overall as the tyre ages?

How many miles / rides do people get out of a front tyre - ball park figure?