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In a this situation should you would you:
A. Do it on the cheap, purchase the expired domain names and redirect to the clients site and use up the old domain until the traffic dries up.
B. Spend more and make somewhat unique content for the old domain and go for future traffic.
I know B. sounds like a good long term ROI rather than the quickie of A., however with all the Pay For of today, I wonder how long term long term is.
A or B?
A mix is an easy answer however I am going in one direction on this one.
If the traffic is minimal, and the listings could be obtained for the original site, I would just take the traffic for now and let it die off.
You could always put some generic on-topic stuff up and use the domains for add'l linkpop.