Thanks for your replies - I am seriously considering developing one or two of my domains - but, I would be starting from the absolutley no experience level.
I am only just begining to get active in domain sales instead of just replying to enquiries as I have done in the past. So at the moment I'm actually struggling to get my head around domain pricing, I have become more aware of just how many of my approximately 1200 domains fit the label of "business descriptives" rather than specific "product descriptives" which seem to be the main stay of the membership here.
I've actually experimented with letting a couple of dozen of my less (in my opnion) valuable domains drop - with the result that approximately 50% seem to be immediately re-registered most by recognised domain professionals - this has moved me back into my hoarding mode, ie, easier to just renew than think about value.