This has to be a really tough call on whether to keep these tubes or sell them. It can be tough to keep tubes that you are not using as you could use the money else where.
Then again, if you ever decide to build an OTL you already have some of the best tubes available and won't have to track them down again.
Yes it is. I think I am going to follow my gut and keep them for now, I just have a feeling I will need them for an OTL design at some point. Some of them are becoming so rare and expensive, I might never find them again.