So I have 30 quilt tops - pieced but not layered and quilted - because I wanted to try the technique. Mastered it and moved on.

I'm in both camps. I'll research and learn for a project I am working on but I will also research and learn about something which I think looks interesting even if I don't think I will do it myself.

My opinion too.

I like to try it on a block. That produces orphan blocks. Sometimes I put all these orphan blocks into a quilt with coordinating sashing. Most of them look great.
If I don't try it on a block, I keep notes or a print-out of it. My stack of such things is getting deep, but even deep stacks don't take up too much room.

It really just depends. Some new things I think are exciting and I can't stop thinking of the possibilities so I have to go experiment RIGHT AWAY. Other new things I just sort of tuck into a corner of my mind for some other time when it seems appropriate.

I do a lot of scrappy and crazy quilts though, so an experimental block or two doesn't turn into a UFO, they just get mixed in with one of my always-ongoing scrap/crazy quilts.

I like learning new things just to deepen the well of ideas to draw from when I am planning a project. I would hate to think I have to make something to represent every single thing I know how to do. :)

When it's time to use something, I can always refresh my memory by reviewing a tutorial or referring to my drawings and notes.

That's me! Maybe shouldn't admit it, but sometimes I will see something I made 10-15 years ago and remember absolutely nothing about making it. But I am proud of the workmanship!