450W/36V = 12.5A
If your motor draws 12.5A continuously, a 10Ah battery should last 48 minutes if discharged 100%; either won't happen, so i think your 43 minutes riding time are good....

Fyi:
The cells in my battery are 40pc. of 3.8V/4Ah. Rated max continuous discharge are 10A; max pulse discharge are 40A. 40 cells means 4 parallel banks of 10 cells. This gives the battery max cont. discharge 40A and max pulse 160A. Max charge rate are 6.5A/cell.
The only drawback ordering from Goldenmotor are the freight price, but i think both US and Canada has distributors...