I continue to think that this concern with the 80% charging is over-thinking the issue. Let's say you don't let your battery get below 20% charge, which is pretty easy to do either with instrumentation or paying attention to the bike's performance and getting a feel for when it has lost significant power. Most bikes today can easily get 25 miles going from 100% to 20%; that may be too conservative but it's an easy number to work with. (My Crosscurrent S gets over 50 miles under those conditions.) If you get 500 charge cycles -- again, this is probably a conservative estimate -- then you've ridden 12,500 miles. If you ride 25 miles every day, then you can expect your battery to last 500 days. Put away a little money -- $5 here, $10 bucks there -- and by the time a year and a half has gone by, you've got enough saved (painlessly) to buy a new battery.
And, with some experience now, fooling around with how to get the most out of my CCS, I've come to agree with Tora -- these bikes work best and are the most fun when they are at full power. If you always lop off the top 20% of the charge, you will never fully appreciate the awesome machines that these bikes can be.
I just got my CCS, with the 17.4 Ah battery, in January. I'm already starting to save for the 52 volt 21 Ah battery. I fully expect to get the most out of the battery I have, and still have a viable battery by the time I'm ready to plunk down the big bucks for the big battery.
But I get it; if some folks want to extend their battery's life as far as conceivably possible, then by all means they should go right ahead regardless of what others are doing. A little bit of math and putting the charger on a timer is a cheap solution, if you don't want to pay the price for a Grin Satiator or something similar.