I don't think anyone meant to imply low, not me, just lower compared to LiFePO4, of course they are lighter, which is good. From what I understand (not a chemist) the lower weight LiFeMnPO4 would expect a cycle life of 1500-2000 cycles rather than 3000-5000 from the heavier LiFePO4 cells. But I could be wrong. 1500 - 2000 is not low life cycle but are relatively lower. (or course neither has been around long enough for most people to really know if either is real)Those GBS cells are exactly what I have in my system - and they are NOT low cycle life batteries, they are rated for several thousands of cycles. For them, you need a BMS like the Elite Power Management system I have (https://www.elitepowersolutions.com/bms) - that has a circuit board for each cell of the battery that monitors cell voltage and temperature, and an over-all controller that talks to all the cell management boards, plus a high current contactor to do the disconnects (I use a TE Connectivity such as https://www.mouser.com/ProductDetail/TE-Connectivity-Raychem/LEV200A4NAF01?qs=R3KmN9Esfyu4S3%2BHsvZmmw==) .
I love my lithium batteries. But I think hooking up a BMS with raw cells is beyond beginner stuff. If I did it over I would probably do a custom system myself.