Everyone has an opinion on what's best for the battery. There are a couple of things that most can agree on, beyond that opinions vary. The number one and two things that can be agreed upon is first don't store the battery at a high charge level and second, don't store the battery at high temperatures. Most information about Li-Ion batteries wants you to store at around a 50% charge. Some say a little higher, some a little lower. This is because problems can occur with the anodes and cathodes at high storage charge levels. Our bikes when at 100% are very close to the max voltage per cell of 4.2 volts---way better to store at a nominal voltage of around 3.6 to 3.7 volts per cell and then charge just before riding. Same thing goes for temperature. Our battery works best at about 76 degrees. So above freezing and below 76 is a good storage temperature. Same goes for charging. Let the battery cool before charging if possible.
As to charge levels, I would run no more than 80% charge level unless needed for a longer drive. On the other end, no less than 30% on the discharge. I know that isn't practical for most but you asked about long life. If you need max range and run under 30%, don't drive at high speed or high power output as you can stress the cells low voltage limit which is around 2.75 volts. On the temperature end, don't run the bike hard when the outside temperature is high as the bike has no active battery cooling system.
The bike needs to be charged for an extended period of time at least once a month to "balance" the cells. Balancing only occurs after a full charge and might several additional hours to complete.
The bike's charger at full output is very low compared to the size of the pack. You could double the output of the charger and still not be close to putting too much current into the battery. So, L1 or L2 charging doesn't make any difference except L2 charging uses less electricity to complete the charge. This is because the DC-DC converter and other sub-systems are "on" when charging. These loads are running twice as long for L1 charging v.s. L2.
One final thing on storage. After getting to the 50% charge level it is important to pull the DC interlock plug. There are several "vampire" loads that run all the time the bike has high voltage DC available even when shut down. If you pull the plug the bike should be at nearly the same charge level you stored it at even if it's a year later.
