I've been thinking about occasionally commuting to work on my mountain bike. If so, I would need to switch out the knobby tires for some slicks.

In this vein, I have also been toying with the idea of keeping two sets of wheels: one with knobby tires and the current mtb cogs and one with street tires and a slightly higher set of gears for the commute on the flat road. I figure that way I can commute to work during the week and still go trail riding on the weekends without having to change the tires repeatedly. (I can just switch out the wheels instead)

Aside from the expense of new wheels and gears, the only other drawback that I can see is that the chain might wear more quickly being switched betweein two different sets of cogs. Is this a legitimate concern?

Any comments or suggestions are appreciated.