The 8 hour charger the instructions mention is not what they send out anymore. Now you get a Sanyo charger that only takes a couple of hours (at least for me). It works really well and, yes, when the light goes off the batteries are fully charged.
I did buy an identical charger to the 8 hour one pictured in the old materials, the dual AA USB charger- the lights stay on forever on that model- no sign of "batteries are done" except waiting about 8 hours. I can check them in the Sanyo charger by putting a "charged" battery in and if the light goes back off after a second or two, then the battery is charged.
I will also say that for anyone who wishes they had the USB model that is pictured here and there, I've got both now (easy to find USB model on eBay, included PoS cheapo batteries) and the sanyo travel charger the MFLB currently ships with is a huge improvement over the USB model in most respects, ranging from construction, materials, function, charging time, etc.
I do like having both for when I need to charge 4 batteries at once, and the USB is cool, so I guess I'm glad I spent like $8 on ebay buying the USB model to go with it.