If we remember that the web is a flattened version of the world, many of our questions are quickly resolved. For example, when moving a website, how should one handle moving from one domain to another or - worse yet - moving pages about within the website such as replacing a topic.
The web is about finding information, and doing so quickly, efficiently and accurately. If your website previously had a page about any topic - let's say redirecting pages - and you wanted to move the page to another position within a new website, the best way then to do so is directly.
If you redirect all of the pages of your old website to your new website's homepage, you will effectively direct all traffic from the old site to the new site, but it isn't a clean, efficient and accurate redirect. The user would still need to fumble through the page to find the information.
The better way to redirect users to a new page is to do so directly so that when they visit the old page, they are taken to the replacement page (the exact new page).
These redirects beg the question... Which type of redirects are best... permanent 301 redirects or temporary 302 redirects. If you plan to undo the redirect down the road, then by all means, you must do a temporary redirect. For all permanent redirects, one should use a permanent 301 redirect code. Permanent redirects are much more apt to be indexed by the search engines and reported in search results than are temporary redirects. The main reason you use a temporary redirect is for true temporary situations in which the redirect will be undone down the road. Temporary redirects also prevent search engines from thinking you were pulling a bait and switch with content in the meantime.
That being said, how many redirects is too many? If you need to redirect nearly your entire website, it is best to use permanent redirects. Matt Cutts tells us that you can redirect as many pages as you need to redirect, and there is no limit. The only caveat to that statement is not to chain redirects unless you absolutely cannot avoid doing so. With that said, we would raise the yellow caution flag to redirecting an entire website. If you need to redirect every single page, perhaps you might want to consider a new domain name; if that's not possible, proceed with caution and care so that all redirects only need be done once. After the redirects are completed, we recommend re-optimizing the content on the website and pushing on your online marketing.