You may find this interesting: http://motorbicycling.com/f16/commut...ing-27937.html
70 miles a day is a serious commute on a MB... not sayin' it isn't feasible - far from it as that's the "normal" mileage I'll rack up on my weekend jaunts, but commuting to & from work is a bit different as you've a time limit lol
How reliable has your bike been? How long have you had it? What's the farthest trip you've taken?
If you had it for a while & worked the kinks out, ride it a bunch w/o issue there's no reason why it wouldn't work *shrug* After all, you've still yer car for backup & those nasty, rainy days heh