If you want the mini motor, go with a 36 volt 15ah Ping, And bring your charger to work and charge there, the mini motor would be easy on the Ping and it should last you @1000 cycles, a lot more if you don't full cycle it every time, so if your trip is 44 miles and the Ping can get 20 miles, then that's 20,000 miles at least out of the ping!
SLA might seem cheap in the beginning, but actually their cycle life for E-Bike use is only around 100-150 cycles, so the ping is a lot better value in the end, + for sla if you have a 20ah it's more like 15ah!
Where do you live dawinksta ? I know I wouldn't ride my bike in winter here, that's for sure!
The minimum I would use on a trip that long would be a 350 watt geared motor, they are more efficient and have more power than a direct drive!
And the Pie will be gutless at anything under 1000 watts, and it's a bitch to pedal!
Mark