That milage sounds about right for a 60AH pack. Does the BMS have a LV cutoff?
EDIT: I "found" the pack that I believe you have.
https://bigbattery.com/products/48v-...golf-cart-kit/
The price is currently $1,200 and I don't know if that includes shipping or not. But for a "drop in" unit the price appears competitive.
I didn't read what the ten year warranty covers or how it would be determined if a unit is covered.
Just a few thoughts. And I'm glad it's working out well for you. Plus....no more battery terminal maintenance!!!