It's funny that you say this, because I took a college class from my favorite professor ever (several classes, actually). He taught about drugs and sex and health, mostly. But his biggest thing he said was that he wanted to make us smart consumers.
He said that if there's only one thing you ever buy generic, make it batteries. I buy generic batteries. Even if they're 25% less effective (they aren't), but even if they were, they're like 1/5 of the cost.
Saving money on the batteries in my flash light doesn't do me much good if the thing won't work when I need it. I guess if most of your battery use involves toys that would be okay. But most of my battery use is flashlight, smoke detector, CO detector, thermostat. I would be willing to put a generic in my tv remote but not the other items.
The few times I bought generic batteries they corroded while they were still in the packaging. Granted I had been storing them for over a year, but I like to keep a lot of batteries on hand for power outages so storage life matters.
I will buy no name car wax, but not no name brake pads.