If you have a Datel voltmeter for example, you monitor as you ride and it tells you mostly what you want to know. You can always take the battery for a proper load test to see what it's "condition" is if you suspect problems. Just sounded like you can't rely much on the Bug, or can interpret properly what it's saying..... and quite frankly, what's there to worry about.... if you have batteries that lasted 5 years, chances are your current one will too, and near the end, do a load test..... Best thing you can do is not let the bike sit and let it discharge below 50% which is around 12.3-12.4. There is a constant drain (small) that keeps the instrument panel functioning when the bike is off.
