My SLA batteries lasted about 7 months then I could only get 2 miles out of them. The max I ever got out of my 60v 9AH SLA pack was 6 miles with moderate pedaling. Now with my 36v20AH lithium, I have yet to reach the maxium range on it without pedaling. I've still breaking the battery in but I've already went 6 miles easily on just 3.5 AH of battery and it's a 20 AH pack !! That means I can go 18 miles without any pedaling on just half the pack. I could probably go 25 miles on 75 % of the pack. That's good enough for me.