Do you know how long it takes before you can disappear from the search engine indexes completely? The technical answer is: As long as it takes for the search robots to return to your site. The real answer is, It could be just a few hours. The search engines will return to your website to crawl it and index new pages and content every time you update it. If you update your site often then you’ll likely get crawled often. Once you train the website robots to return to your site every few hours or so then they will do so by habit. They’ll get used to new content on your site and may even crawl it if you haven’t updated it.
On the other hand, if you never update your website then you’ll slip in the rankings. That slipping, however, will likely be a gradual falling away. But it really depends on how often your competition updates their websites. But the real serious issue is when your site is taken off line completely. If you take your site down for maintenance or to update it, or to clean out malware – for any issue really – and fail to republish it in a reasonable amount of time, when the search engine robots go to crawl that site and find no content, you’ll be de-listed. When will that be exactly? No one knows.
Technically, it will be on a quasi-scheduled bot appearance determined by how often the robots typically crawl your site. If they show up every six hours then it will likely be about that long, give or take, since the last crawl. Again, it depends on how often you typically update your site.
The lesson here is don’t take your site off line for an extended period of time. Otherwise, when you do republish it, you’ll find yourself clawing to get back to the rankings you had when you were de-listed and it could derail all of your hard word and ongoing search engine optimization efforts. It won’t take as long to regain what you lost as it did to get it in the first place, but why would you want to go through that?
If you have to take your site down then at least work on getting those social networking profiles built up. Diversify your presence online so that if you lose one site then you’ll have plenty others to take its place.