Ouch!!!
Eneloops will be your friends.
Those blue ones are over ten years old.
-Pat
I think to a large extent, is just pure pot luck, I've had some old Every Ready D cells that have been installed for over 20 years and not leaked, likewise Duracell for around 10 years with no bother at all, YMMV.
I think it’s likely a combination of several things, as in years (ok, decades at this point) past, I rarely had a Corrodacell leak, but in the last 10-15 years or so see it alarmingly often. I have a photo of some that began leaking in their retail package (bought from Home Depot, so not of sketchy provenance) while still several years shy of their 'best by' date.
I suspect it’s likely due to a combination of corporate bean counters and environmental regulations - the bean counters for 'value engineering' things to use the least possible amount of material in their construction, and the new regs for changing the chemistry and making it more corrosive. The problem seems worse in the smaller cells (AA, AAA) than the bigger ones - maybe because so many are made they’ve been 'optimized' more (read that cheapened further), or being physically smaller sealing isn’t as robust and/or any internal pressure build up has less room to expand into so is inclined to squirt out sooner.
Like you, I’ve come across older ones that are dead as a door nail yet still sealed up, but far too many of more recent vintage have puked alkaline schmutz into things for me to trust them at this point. I first learned of the Eneloops on a photography forum in 2010ish, bought some to use in flash units which tend to go through AA cells at a rather costly rate, and have been using them since then as much as possible. There are a few things that don’t like the lower voltage (my good stud finder, for instance), but wherever else I can do so I use them now. While it’s admittedly a very small sample size, none of them have yet leaked on me, while in the same time frame I’ve seen too many Duracells puke their guts out.
-Pat