there is no line crossed at 81%. Only charge to what you need which includes a buffer. 20% is fine. 19% is fine. 21% is fine.
I guess my question could have been phrased more clearly. What I'm really asking is: whatever you do on a regular basis to try and slow down long-term capacity loss - keep the battery between 80% and 20%, keep the battery between 60% and 20%, straddle 50%, charge daily to ensure the lowest possible DoD, etc. - which SOC should you go by when doing this, the dash or Leaf Spy?
First off; you need to evaluate your needs and willingness to charge publicly.
The ideal situation is to straddle 50%. Avoid "any" time at the extremes (under 10% or over 90%) but again, no line here. If you are taking a trip, the convenience of a full charge far outweighs the slightly greater degradation you get from it. Degradation is not avoidable so it is all about balancing needs.
The only real red flags are high SOC AND heat. That is the worst situation. Now fast charging on a hot day but immediately driving away is probably better than charging at home then letting it sit a few hours before going anywhere. Its the time at high SOC that is the killer. Heat makes it worse.
With public charging, some are free, some are cheap and some are expensive. You want to know ALL your options on your routes. Plugshare.com is a good place to start.
If you are not into public charging, then get LEAF Spy. It allows you to know exactly how far you can drive. LEAF Spy is dirt cheap when compared to the stress LEAF instrumentation causes.
The following is personal opinion somewhat based on experience. I am ok with taking LEAF down to the last 5% SOC pulling into my garage. My 2013 probably came home under 15 GID maybe...100 times, maybe more than that. If that happens, no worries, plug in for an hour soon as you get home.
Each LEAF pack has acted differently (2011 and 2013 were close to the same) for me but my best pack by a HUGE margin was my 2016. Part of it was due to short period of time (14 months) but negating the miles driven (29,413) or QCs (275) the only real difference was it was first LEAF that had NCTC so I kinda went crazy on the free charging. My job helped as well but I was literally fast charging 2-4 times a day in Summer, getting home at 20-50% SOC and 10 (sometimes 11 temperature bars) The next morning, I would hit the QC and start my rounds for the day. This lasted 6 weeks while servicing a client who had 65 clinics in the region that was spread thru out the Olympic Peninsula down to Oregon. It was the perfect LEAF job as I had 15-45 mins of paperwork between each job and some days had as many as 12 jobs scheduled. So yeah, long hours but my charge time was being billed to the company since I was working. It was lucrative.
Anyway, 3 days before the 2016 was wrecked, I went 116.2 miles on a charge in January. This pretty much illustrated that I had "minimal" capacity loss. But the major change was much less full charges and a LOT of living in the middle. My charge time frequently was based on how long it took to do paperwork. Realize I was doing 14-25 hour days so sitting around was not an option. So it was a lot of plug and run which meant cycling from 20 to 70-85% several times a day.
TBT; I didn't charge overnight a lot of times due to having 11 temperature bars. I felt it better to let it cool off overnight and then grab a charge in the morning.