I've read up on the batteryuniversity.com website and hear all the claims about li-ion batteries but in real life experiences of mine, they last longer if I at least try to discharge them all the way between charges. Even the manufacturers recommend complete discharges every 3-4 charges. The whole argument of "li-ions don't have memory" is false. My camera, laptop, portable DVD players, phone batteries etc are all li-ion and I discharge them completely every chance I get, even if it means I will hve to without it for a bit, but i'm fairly prepared and have spares or portable chargers. My iphone 3g is 6 years old with original battery, and I still get 4-5 days between charges (when I don't used Bluetooth and internet often). My camera battery is 4 years old and performs flawlessly (thousand of photos between charges). I also have a number of li-ion batteries for my fancy torches (18650's and 14500's) and once again I discharge them completely because they last longer and have better capacity long term. I paid too much for those 18650's to ignore them.
I also do the same with my 90 or so Eneloops to ensure long life.
I short, no matter the chemistry, I completely or almost completely discharge my batteries every cycle and keep them fully charged in storage where I rotate them. I've got a lot of spensive batteries I like to keep in tip top shape. I do have smart charges and charge properly, that makes a big difference too.
As to the ebay cheap batteries, you get what you pay for. However Battery World have a large range of their own branded aftermarket batteries for camcorders which are comparable to original batteries. Maybe check them out.
cheers