- Their shelf life is usually much longer. Corollary is, if you can find some that have been stored, even for a rather long time, they are immediately operational. Can be a life saver. Related fact is that rechargeable batteries are likely to be discharged at the very moment you need them. Especially true for less often used items.
That was true 25 years ago but times have changed. For more than a decade already almost all NiMH cells have been the low self discharge type, they come pre-charged and hold a substantial charge for years. I've left them in a seldom used flashlight for at least 3 years and they still had plenty of charge left. I've had brand new alkaline cells leak faster than modern NiMH cells self discharge.
https://en.wikipedia.org/wiki/Nickel–metal_hydride_battery
The low self-discharge type has been introduced in 2005, so that's 15 years ago, not 25. Those cells are pretty good indeed, although with a slighly lower capacity as a trade-off. But even to this day, not all NiMh batteries on the market are of LSD type, far from it (and the average joe is likely to buy non-LSD batteries, because those are cheaper and because they just don't know... or even just because they will tend to go for the highest capacities, which look attractive, which are likely NOT to be of LSD type.) As an example, a typical capacity for NiMh LSD AA batteries is 2500mAh, whereas you can find NiMh AA batteries up to 3000mAh, which are unlikely to be LSD IMHO.
Standard NiMh batteries OTOH still have a relatively high self-discharge rate.
I've never seen a decent-brand alkaline battery leak within a couple years. If from a major brand and stored properly, their shelf life is longer than 5 years usually, 10 years is not uncommon.
A corollary point, but not directly related to shelf life point I was also making is that, due to our habits and a bit of Murphy's law, random rechargeable batteries stored in a drawer are likely to be depleted when you actually need them (partly because of self-discharge, but even with LSD ones, just because you're likely to have stored them discharged unless you're very disciplined.) I for one have a few primary batteries in drawers (never used), but pretty much all secondary (rechargeable) batteries I have, I've used them at least once (I think storing brand-new rechargeable batteries for extended periods of time would be relatively unusual, compared to primary batteries.) So this point was not just about technology, but about the practical aspects.