Mountain bike tires going bald after few weeks A few weeks ago I bought a decent mountain bike. It's not a fat tire bike but it had pretty wide and grippy tires. I rode almost 200 miles over the past few weeks on asphalt but tires are going bald. I don't go mountain biking with it, I only use it on the bike trail which is asphalt. There is not much left now.

I am wondering what did I do wrong? is it normal? If I change the tired how long will they last? 

Thank you.
'Decent' MTB means different things to different people. What are the actual tires' make/model and sub model? 

Many manufacturers use the same tire mold for different tires with different characteristics. For instance Schwalbe make a range of tires (e.g. Nobby Nick, Racing Ralf, Rocket Ron) with various tread patterns for different terrain. With each in this range you can get various sub models. Apart from light weight vs puncture protection, there is 'Performance' and 'Evo' rubber compound. Evo does not last long, but holds on like a pitbull with a bone; Performance lasts longer, but is less grippy.  (Using Schwalbe as an example here, not a recommendation)    

If it is a high end bike, it's likely come with tires built for grip in loose surfaces, not longevity on paved surfaces. These tires have a soft rubber and wear very quickly on paved surfaces. 200 miles from MTB tires is not great, but not unexpected if they are a 'race' model. 

For your next set of tires, look for ones designed for hard/paved surfaces, and unless you need (or want) the 'race' performance, go for model designed for longevity.  

Most tire manufactures have good tools for tire selection on their web site, otherwise your local bike shop (LBS) will be able to recommend a tire suitable for the riding you are doing.