Just so you know, lithium batteries lifespan is best when kept at a neutral SoC. That means somewhere in the 45 to 50% range. Keeping it plugged in to maintain a SoC that is above that will not help retain battery life.
Ways to increase battery life:
1. Avoid leaving the battery sitting at a low or high SoC for a long time.
2. Schedule charging so its done just before you drive it. This limits the high SoC duration.
3. Don't expose battery to high temps. Ideally it doesn't see above ~85F, but park in the shade to help when that can't be avoided.
4. Avoid high depth of discharges if possible. If you do a 20% discharge daily vs 60% discharge by charging once every 3 days, the former will allow the battery to likely last twice as long in terms of charge cycles and number of miles the battery allow the car to be driven.
I'm not listing age, which we can't do anything about. But cells degrade over time, and we can't avoid it (Other than keeping the battery pack on ice to slow it)
If you doubt this post, check out the neat charts on battery university:
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
The absolute worse thing to do is high SoC + high temps. You can't use blanket statements like "90% is better than 100%" because 90% in 30 degree weather is absolutely less stress than 80% in 95 degree temps.
The items I listed above are general rules of thumb, you obviously can't avoid them all, but knowing what is harmful to a battery is useful for situations when you can avoid them.