So lets say you change all of your urls on your website to a completely new url structure. You 301 redirect all the old urls to the new ones. So how does it take for this to update in Google and other search engines? A thread on WMW has some good thoughts from members who have experienced this situation. The thread starter remarked on his situation:
We dropped from 120k pages in the index to 87k pages. We also are not coming up for certain keywords that we were always there for, and are seeing 50% less traffic from Google.
Some of the other posters said that it take quite some time up to a year for all the urls to be fully spidered and ranked again by Google. It is important to mention that result will vary based on a number of factors. If you have a site that has 120K pages and you change all the urls, then it not unreasonable to expect a large delay. It often comes down to "Is it worth it to change that many urls?" Does the outcome of such a change benefit you in the long run? For traffic from search engines? Or for visitors?
"My experience was that, long term, it was always a positive step. Short term, a site with anything lower than a PR7 Home Page may experience a few bumps on the way to improvement. It's essential to get the technology right in your rewrite scheme, and there are several pitfalls.
1. Poorly configured, you may open the door to duplicate urls for the same content. 2. Remember that there are two steps to address: a. get the new urls to resolve and b. 301 redirect the old urls. 3. I found it more effective to do a ranking, traffic and backlink study and then only redirect the key urls, letting the rest go 404. That approach seemed to give the quickest "recovery" time in Google I ever achieved. In fact, that site never saw a dip in Google traffic, and then rankings improved quickly."
Some great advice from him. Continued discussion at WebmasterWorld.