I know what a keyboard obsession looks like. I have around a dozen mechanical keyboards in my house that I don't use on a regular basis. I usually switch between two or three models that I really like, but the rest are safely tucked away in their boxes, stored in one of two designated locations. This made me think about whether I should finally let go of some of them, and put them to better use — giving them to someone, using them when traveling, or raiding them for keycaps and switches.

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5 Use it on a secondary machine
One that you aren't emotionally involved with
This one is obvious, but if you have an older PC that you use as a retro gaming build or home theater PC, you can use one of your old keyboards with it. An unremarkable wired keyboard usually works great on such machines — you don't need to worry about keeping it charged, and it's always at the ready.
Many people are tempted to buy another keyboard for their secondary PC, especially if they're into mechanical keyboards. You can resist the temptation and use one of your older boards instead, not only saving money but also the environment. Chances are, your old keyboard still works without any problems. You probably moved on because you found something that typed and sounded better, but your older keyboard can still serve, just on a secondary PC this time around.

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4 Gift it to friends or family
You don't need to hoard everything

Often, one of your loved ones can make better use of your old hardware than you can at the moment. Giving away your old keyboard to a young nephew or niece who's building a budget gaming PC is a great idea, and so is gifting it to a friend who needs a lightweight keyboard for their on-the-go needs. Not everyone likes their laptop keyboard, so your older mechanical keyboard might enhance your friend's typing experience, and they'll love you for it.
You could also make it the latest addition to a family member's PC, introducing them to mechanical keyboards. I recently gave my Lofree Flow Lite to a friend who was putting together a budget gaming rig. I have other low-profile keyboards at home, and the Flow Lite is a great minimalist keyboard for most people. Giving away tech keeps it from the landfill and ensures you're making the most of it.

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3 Use it as a travel keyboard
Only the lightest will qualify
You can use your old portable keyboards yourself by taking them on your work travels. I love typing on my mechanical keyboards, but not all of them can double up as a travel keyboard. The lightweight and low-profile models, however, are perfect companions on those relaxed work trips where I don't like to have too much weight in my backpack. I'm already lugging around a heavy laptop, so the more bulk I can cut out from the peripherals, the better.
Most of my old keyboards support both 2.4GHz and Bluetooth connections, so connectivity isn't an issue. And their battery backup is enough that I can get through three or four full days of work on a single charge (usually, they last longer). If I have a designated portable keyboard in place, I'm often more willing to work away from my desktop, and that does wonders for my productivity.
2 Turn it into impressive wall art
Let the creative juices flow
If you aren't too keen on reusing your old keyboards in the traditional sense, you can always transform them into conversation starters. Maybe your old keyboard has a few faulty switches, dirty keycaps, and a dented case, and you don't want to restore it to its former glory. In that case, how do you feel about taking it apart and making it a permanent part of your PC room? Maybe you could spell your favorite quotes with the keycaps or create portraits on your wall.
You could also fashion wall paintings out of individual components of your keyboard, such as the case, PCB, plate, and foam. The keycaps can also be used to create a world map or other art on the wall, or simply used as thumbtacks if you aren't in a creative mood right now. You could also turn your entire keyboard into a lightshow by affixing it to the wall, powered on.

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1 Salvage keycaps and switches
The circle of life
Finally, you can at least extract the keycaps and switches (and other internals) from your old keyboards, and use them on your current keyboard for a breath of fresh air. Maybe you're bored with linear switches and want to revert to tactile or clicky switches present on one of your older keyboards. You could also swap your keycaps for your older ones, or mix and match to create a Frankenstein keyboard.
As long as you have a hot-swap keyboard that supports the switches and keycaps from your older keyboards, you can go crazy with it. Personally, swapping keycaps and switches is always a relaxing activity, and I enjoy creating new looks for my keyboards. Instead of throwing out my older keyboards or giving them away, I can retain them and use their components on the models I'm currently in love with.

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Learn to love your old keyboard again
If you often change peripherals, storing all your older models can become a minor annoyance. Keyboards, in particular, take up a lot of space, and if you don't find new uses for them, you're only left with a few choices: sell, donate, or recycle them. Instead, you can keep using your old keyboard on your older computers, gift it to a friend or family member, use it as a travel keyboard, or take it apart for switches and keycaps.