Yeah I have a speak n math that takes like 4 C or D batteries or something ridiculous and lasts 10 hours according to the manual. The toy is basically a glorified calculator so I don't know how it uses that much power (must be a lot of power processing in there or something...)
In the past Alkalines were a far better at not leaking when compared to the Carbon Zinc alternatives.I remember they put stickers on almost all toys that said Kb recommends alkaline batteries.
Norm]These cells have a short shelf life as the zinc is attacked by ammonium chloride. The zinc container becomes thinner as the cell is used, because zinc metal is oxidized to zinc ions. When the zinc case thins enough, zinc chloride begins to leak out of the battery. The old dry cell is not leak proof and becomes very sticky as the paste leaks through the holes in the zinc case. The zinc casing in the dry cell gets thinner even when the cell is not being used, because the ammonium chloride inside the battery reacts with the zinc. An "inside-out" form with a carbon cup and zinc vanes on the interior, while more leak resistant, has not been made since the 1960s.
I am sure the manual specifically mentions alkaline as most toys did back then from what I remember. Getting parents to buy the right batteries was tricky due to the price points. Also KB toys had a massive campaign to recommend only alkaline batteries at that point as I remember they put stickers on almost all toys that said Kb recommends alkaline batteries.
I just had an AAA Duracell leak with the expiry date (or best used by date) for March 2017. It didn't leak much, the cell is still holding 1.5 volts. It was being stored but now i just threw it in a light but keeping the cells out of the light when it's not being used. I'll probably get the cells drained out in a few days.
You're taking a risk using alkalines that have already started leaking. The more alkaleaks are drained, the more hydrogen gas builds up in them to push that corrosive goo out even more.
Give your alkaline collection to someone you really hate.