Thanks for all your input - tedster, you're right in that it depends on what we are doing. Effectively we have a type of catalogue, with a high turnover of product! A 301 is not an option as all the content is different, I can't get away with saying it has moved..
I like the idea of keeping the content for a short while.. or potentially forever as long as there are related items and / or a search option above.
The link juice is something that could be annoying. If I have a couple of links on the 410 would they count.. I think not!