Thanks for the responses guys. I assumed as much. I think I'll leave these domains on the shelf until such time I can develop them (if that is going to be a worthwhile investment of my time).
The prime reason for owning them is protecting IP, and retaining competitive terms in my portfolio.
I do have some domains that have good keywords, which I've already developed, albeit with only a little effort.
These seem to rank well after a year or two, and I feel those sites that have been developed to a minor degree will be good candidates to 301 redirect.
Thanks again.