That is alot. I'd suggest:
1) If possible, remove those with no searches (ask overture to tell you which ones this is - it's their sever space after all).
You may be wasting time reporting etc on them - if they don't get searches, they don't work.
There's a danger of leaving them in "just in case" and not seeing that:
1) your time costs money to manage them
2) even if they get an occassioanl click, only a percentage of visitors convert, not every one - when will they get enough click to covnert?
3) So if you evalaute the cost of your time in relation to the financial benefit these keywords might, just might, one day eventually bring, you may well decide they are a waste of time
4) If your margins allow you to, raise your bids on converting keywords (assumming your are ROI tracking). The 80/20 rule (approximately) applies - 80% of success from 20% of your keywords...
Hope that helps.