Best case scenario for a battery stored at 40% SOC at room temp will lose roughly 4% capacity per year:
https://batteryuniversity.com/articl...ased-batteries

96% capacity at year 1
92% capacity at year 2
88% capacity at year 3
85% capacity at year 4
81% capacity at year 5
78% capacity at year 6
75% capacity at year 7
72% capacity at year 8

Rule of thumb is that a batttery has reached it's serviceable life at 80% capacity which is close to the 5 year mark

There are other factors which reduce a batteries lifespan too, most of my packs last between 6 months to a year where I race in triple digit summers in Texas