How best to redirect URL from expired classified ads?

[Donaab]

We have problem because our content are classifieds. Every ad expired after one or two mounts and then ad becomes inactive and we keep his page for one mount latter like a same page but we ad a notice that ad is inactive. After that we delete the ad and his page but need to redirect that URL to search results page which contains similar ads because we don't want to lose the traffic form that pages.

How is the best way to redirect ad URL?

Our thinking was to redirect internal without 301 redirection because the httacces file will be very big after a while  and we are thinking to try a canonicalization because we don't want engine to think that we have to much duplicate content.

[Bevelwise]

If your classifieds are categorized in any way then after a listing is expired I would always 301 redirect it up to the relevant category, but I think it would be more relevant to 301 it to the relevant category than trying to decipher a similar specific listing.  I would find a way to dynamically after a listing expires it implement a 301 redirect.  I don't believe canonicalization is going to help here unless you have other duplicate content issues with the site.  I would not worry about the size of an .htaccess file because it doesn't impact anything negatively.