Its all about perspective. Some considered my 2016 as high mileage despite having just under 30,000 miles on it but it did have 4 periods of 2+ weeks when it wasn't driven and I only had it just short of 14 months.
I haven't had any LEAF longer than 3 years (4X Lessee here) so hard to comment on long term durability but can say, you can help yourself by maintaining your tire pressures AT the max sidewall pressure listed ON THE TIRE
Rotate your tires every 5,000 miles AT A MINIMUM
As far as the battery goes? I pay the least amount of attention to this, electing to prioritize my needs first. So my "habit" of multiple QCs during the hottest part of the day, 10 or more temperature bars, etc... (On the 2018 LEAF, the temperature bars are on their own screen so its easy to ignore them. a VERY good idea).
But there are some basic guidelines to BMS that you should always keep in mind.
**Don't generate unnecessary heat. Park in the shade. Its laughable how available the shade parking is around here because its 100 feet farther from the building. I can literally take up 3 spaces without any issues whatsoever. FYI; the heat generated from quick charging is "necessary" heat. a BIG difference.
**Avoid L2 charging during the day, especially if its at work in an uncovered parking lot and you are only doing it because you don't want to add to your electric bill. Why is this different than QCing I do? Because I rarely charge over 90% and I immediately drive off. Now I hear people say, I plan my charge to drive off as soon as the charge is done but the logistics say that you will spend well over an hour (probably 2 or 3) at greater than 95% SOC both coming and going. Not good especially when you are only doing it to save $3 on your electric bill.
** Charge only to the level you need. Now with older LEAFs, this advice may not apply but if you have a 2018, then its rather easy to say no to "Do I need to drive 150 miles today?" So don't charge to full if you will be getting home with 60% of your pack left. Now, it sucks that Nissan didn't allow custom charge levels but you can play around with the charge timer to get a lower starting SOC.
Finally; it should be rather apparent by now that the reason new pack prices have gone up is because refurbished packs will soon be on the market and they have to sell for enough to be profitable but at the same time, cheap enough to be a viable option over new pack prices. So the buy lightly used for $10,000 over buying degraded for $7000 and spending more to get new battery scenario is not viable OBVIOUSLY so why anyone thinks that is what is going to happen is....
well, par for the site, I guess.