I'm a stationery person that come from the using it and not the collector perspective.
Most of us end up buying stuff you don't end up liking or using for what ever reason. It might be that you didn't like it after all or that you were into something for a long time but found something that worked better or that you got it for a use case you no longer have. The reason for it isn't that important.
Here is my process for this, it is more of a process I use for everything in my apartment. I try to do this every couple of months. I collect everything that is either junk or stuff I don't feel is necessary. The latter is usually things I never use and don't have any emotional attachment to. I just put it all in a giant pile in the middle of my kitchen / living room.
Then I first sort out all the junk and put it in bags and throw it out. Then I put the rest in bags and tape a piece of paper with a date on it and put it in my storage unit.
I usually throw stuff out because I don't want to deal with selling a ink bottle or $20 pen. Seems like too much of a hassle. It would be different for a $100 pen. You may have different reasons for doing things differently.
Now. Two to three times I year I start with the stuff I've been storing for the longest without recovering it to my apartment and have been in the bag for at least six months and fit as much as possible of it in my car and throw it out.
I'm very much of the opinion that you should not keep stuff for sake of keeping it.