Most of the time I have two quick links on my Rohloff bike. I have to remove four links if I want to use a smaller chainring and two quick links simplifies that. (Photo)
I carry a few spare quick links on tour. Once years ago working on my bike at home outside, I disconnected the quick link to remove the chain and one quick link went flying, I never found it. You do not want to be on a tour and lose a piece of your chain. I carry several spare quick links on my tours.
One tour, one guy I met had broken his chain four times, his chain got shorter every time, and he was getting to the point where he was running out of gears. I gave him one of my 8 speed quick links for his 9 speed bike and said it would probably not work, but if he was stranded on the side of the road, that would be the time to try it. This was in the middle of Iceland, nearest retailer of anything was over 100 km away.
Some quick links are useable for multiple times, some are for one time use. If possible, avoid the one time use ones.
If using KMC 8 speed chain, there are two different quick links, a 7.1mm and 7.3mm, get the right one.
Do you have a tool to remove a quick link? New ones sometimes need some help from the right tool. I bought a small version to carry on tours.
On tour I also bring a chain tool, but that is because it is attached to the better multitools so I would have to go out of my way to leave it at home.
Off topic but related - If you are getting a Thorn built, they would have the spare spokes and know what sizes you need, buy a couple spares. You probably will never need them, but if you do it is nice to have the right length spare already. On tour I carry two spares for each wheel.