I've recently started thinking about what to do with my current mobile devices — an original iPhone SE and an iPad Mini 4, both bought refurbished — once they stop receiving support from Apple. That might be happening very soon, depending on what the hardware requirements will be for iOS 15.
We already have one other iPad still soldiering on despite no longer being supported — my mother's iPad Mini 2, which was an incentive for a newspaper subscription several years ago.
These devices are still in good working order, with little wear or tear, and the only limiting factor on their lifespan is their batteries, which will eventually lose their ability to retain a charge.
I've looked into recycling and trade-ins, but the amount of money I'd get back would be minimal, and I'm wary of throwing away electronics that aren't broken.
The iPad Mini makes for a nice ebook reader and radio / music player, so I could definitely see myself repurposing it as a bedside companion.
The iPhone SE is somewhat more limited due to its lower storage capacity of 16GB, but its small size would make it a very pocketable iPod.
I'm still undecided as to what would replace them as my daily devices. I really hope that Apple keep the iPhone SE around, as that would suit me just right size and price wise. The iPhone 12 mini might be a contender, if they keep it around and reduce the price when the iPhone 13 range is launched. The iPad situation is currently a choice between the iPad Mini 5 or the latest iPad Air — originally, I was leaning towards replacing my current Mini and keeping most of my accessories, but the Air would give me more options and probably have a longer lifespan.
But those are decisions for another day. I've stopped having gadget lust, thank goodness.