Generally speaking self discharge of lithium ion is very, very low. Somewhere around 1% loss a month.
I turned off my seven Leaf module e-assist cargo bike on 03-12-20. The bike had been charged to 58.2 resting volts, and ridden 40.8 miles down to 57.7 resting volts. Thirteen months and one week later, four weeks after getting vaccinated, I turned it back on. The Cycle Analyst read 55.1 volts. I rode the bike down to the 44.8 volt cutoff. The resting voltage, after a half hour, sat at 45.5 volts.
I had put 40 Ah into the pack, per my Satiator smart charger. My last ride had used 14.9 Ah. The ride this week used 19.7 Ah. So it appears the pack lost ~5.4 Ah, or 13.5%