LFP pack still at 100% after three years, is that normal?

I've had my LFP car for three years and 48,000 km, and the health readout still shows 100%. My previous NMC car had clearly dropped by this point, so I'm suspicious the number is just a placeholder. I charge to 100% at home roughly twice a week, rarely fast charge, and park outside in a cold climate. Anyone seen a proper capacity test on older LFP packs? I know the flat voltage curve makes estimation hard, but I'd like to know whether my range loss is hiding behind a rounded figure. What's the best way to actually measure degradation at home?