We recently launched a redesign/redevelopment of a site but failed to put 301 redirects in place for the old URL's. It's been about 2 months. Is it too late to even bother worrying about it at this point? The site has seen a notable decrease in site traffic/visits, perhaps due to this issue.

I assume that once the search engines get an error on a URL, it will remove it from displaying in search results after a period of time. I'm just not sure if they will try to re-crawl those old URLs at some point and if so, it may be worth it to have those 301 redirects in place.

Thank you.