Dead Battery or Something Else

[Lez72]

I would say it's defiantly the battery. People seem to get different service life out of their batteries depending how they have been treated. One Yuasa battery may last 5 years but another might last 10. From the fact that when it initially died and you charged it enough to show a healthy charge which started the bike doesn't actually mean it was in a healthy condition. Some chargers are ambiguous at best. I generally trust how the battery performs over what my Optimate says.
The symptoms you speak of and the scenario you provided point straight to the battery for my money.
A few months ago I had issues with my car battery. I took it off and charged it. The battery itself has a green light displayed when it's in healthy condition and fully charged. I charged it overnight until the green light was displaying and put it back on the car. I then had the doors open for 10 minutes so the interior lights were on. After the 10 minutes the battery had totally discharged and wouldn't start the car. A healthy battery would last far longer than this. I fitted a new battery and the problem was solved with no issues since. Even if I leave her for a couple of weeks she will start without issue.
I feel certain that a new battery will solve the problem.