It's not just opinion and wives' tales out there--there has been scores, no, hundreds of detailed, controlled, scientific studies and analyses of this battery chemistry, as well as huge resources used to develop and characterize them. What people have posted are not off-the-cuff 'personal experiences,' but references to the results of these substantial efforts in developing and understanding batteries.
Also, it is well-known that many cheap-o Li batteries (like the ones you buy from eBay for under $10, or other aftermarket products) are cheaply made and may not hold/maintain a proper charge. (Were your batteries name-brand ones, or "made in China"?)
My suggestion would be to charge and synch whenever the mood strikes, and to not let the meter get below 2 bars for very long before charging. But it's your Reader, so it's your call.
