Well Stacka, there was a time I lived in the bush without conventional electricity, however I ran a lot of stuff in my cabin with 12 volt DC. Having said that I learned a bit about chargeable batteries. What I found was that automotive batteries (which includes bike counterparts) were good for at least a few total discharge cycles, or flattenings as you put it. The average automotive battery could suffer perhaps 8-10 total discharges (cycles) before becoming less effective at holding a charge. A better battery for my cabin's 12 volt requirements was a marine battery, or one made for an electric golf cart (what's known as deep cycle batteries), as those batteries could go from being fully charged to flat maybe a couple hundred times before showing signs of deterioration.
I can boil it by down by saying that the average lead/acid based bike battery can take a flattening a few times (not just one) before it's not longer useful. But once fully drained it is advisable not to leave it in that condition for an extended period of time. Doing THAT can kill a battery.
Today's sealed gel batteries are very good and maintenance free. There are so many brands out there but I trust most of it. I'd go for one that you have to add the acid yourself to the cells after you buy it rather than one that is ready to go off the shelf. That way you know it's 'fresh' and hasn't been sitting in a readied state for who knows how long.
Hope this helps... btw, for my 4 wheeler I use a marine battery over a regular car battery. It's a logic left over from the cabin-in-the-bush days when I would park my truck beside the cabin and plug the truck into the awaiting umbilical cord. The marine battery lasted longer (for cabin purposes) while providing all the crank power I needed for the truck.
