While Mining is a hot topic I guess it's a good time to reintroduce this thread to everyone showing how long it takes to get to each level, your mining speed for each level, and how many rocks you'll be mining over that time.

http://www.era-go.com/forum/showthre...ng-Level-Guide

It says going from level 50 to 51 will take the longest as your fast mining speed will actually outpace the extra rocks added for going to the next level.
Also, if you actually do make it to level 100 you'd have spent about 1500 hours mining.