I have a Wilderness Energy brushed 36V. I had to replace the connectors and rack. The kit has been durable and still works after 3 years. It is a low end kit but has served pretty well for the price.
With any electric bike, the most important part is how you mount the batteries and the quality of your connectors and switches.
If you can, find out if you can run the kit on 48V. 48V has much better power than 36V. I was able to just add a battery in series and it has not blown the controller. Word on the street (visforvoltage, endless-sphere) that the brushed controllers can handle at least 48V.