I hadn't had it on a tender for a couple of weeks, I have been riding every two or three days and the battery always felt fine.
When we set off to the beach the battery felt fine, it was only this morning when I started her up to come back that the battery felt a little sluggish.
I have done 100 mile plus rides a few times with no issues so far, this feels like a new issue to me.
The last time I did put it on the tender the battery said it was fully charged after, I think, about four hours on the tender.