Let's do some basic math here. Assume you get 20k experience per hour it would take about 650 hours for 99 mining. I know 20k experience is low, but I guess thats at worst and assuming you're botting. This is 27 days worth of mining straight. On the other hand if you're power mining like a pro, you could pull 40-50k experience per hour, this would drop the time getting 99 by more than half (less than 13 days). So overall, yes, it is definitley possible getting 99 mining in 1 month.