The typical question that gives many SEO professionals a bit of a gut-check is, "How long will it take for you to show me results?" Typically, the answer will vary based on the age of the site in question and the level of competition for high volume keywords, if boiling it down to two major factors.
However, there are considerably more elements to a fully-fledged answer. These are also split into new vs. redesigned or reformatted (URL) Web site.
When dealing with a brand new domain, it will likely be difficult to gain the necessary "trust" for rankings for broad competitive terms for at least three months, but often closer to six to nine months. This isn't always as clear cut -- if you have and continue to put out useful content, and if you're fortunate to benefit immediately from authoritative and consistent links (or are willing to cheat), you could see results sooner.
Of course, if your technical infrastructure doesn't support good crawling of your pages and understanding of your content, you'll be dead in the water before you even start.
When dealing with either redesigns or post-launch SEO, the best thing to do is never give, or accept, a response "from the cuff." Setting unrealistic expectations will only lead to disappointment. Not only should people take time to project the best and worst possible scenarios, but these projections should be updated post-launch at least once, as crawling and indexing patterns get established.
How Quickly Do Search Engines Crawl/Index a Redesigned Site?
Recently, we helped relaunch a fairly large site with thousands of pages. A major directory level was gone, and it wasn't possible to implement all redirects prior to launch.
Within 12 hours, Google had indexed and was returning well over 1,000 of the new pages in its results. We started seeing a few dozen new pages in each directory level off the root that we were monitoring, within about four hours after launch. I can't claim as dominant of a performance by Yahoo, and look forward to our first Bing-monitoring, which has to be better than the last.
The catch to this process is that, at the same time, the search engines are ridding themselves of any no-longer used URLs, through new robots.txt files, 404 errors, and in a pattern that appears to indicate an "as we can" programming attitude. They will also continue to index those with rankings, fortunately.
If the site relies on a lot of home page rankings for top keywords, then a redesign usually won't hurt, even if the new home page URL now resolves to the root instead of a prior directory-appended version, based on a number of sites.
How Difficult is it to Maintain Current Rankings After Launch?
For new domains, brand terms should rank nearly immediately after the first crawl -- maybe not first however, as Rosetta experienced after launching and finding Apple and the language software ahead. A unique brand name should have relatively no problem ranking number one very soon.
Benchmarking is crucial to understanding how post-redesign crawling behavior is treating a Web site. Monitoring "cherry" keywords, such as the top 10 to 50-plus branded and non-branded referring terms, and measuring them by search engine, can give you insight into this.
This is also an important high-level indicator of how much the search engines initially trust your new domain structure. It happens a lot quicker when you're shifting URLs on the same root domain, than when you're moving to a new one.
How is Traffic Affected After Launch?
The classic answer to this question is often unfortunately accurate. There's always going to be at least a slight drop in traffic, even with SEO.
On a percentage basis, this can equal dozens, or even hundreds of traffic-driving rankings. The better you do with maintaining your high-volume keywords, the more likely the dip may be being caused by other factors as well, including an unexpected or seasonal dip in branded traffic.
The best ally in monitoring post-launch success rate is, of course, analytics. As long as it's been properly configured, very important data can be gleaned from 404 reports and high-bounce pages or referrers. Google Webmaster Tools and Yahoo Site Explorer are important allies in the quest for new or continued rankings.
Lastly, level of implementation is probably the single worst enemy to SEO success. Lack of SEO implementation is so dangerous because even what seems like the smallest de-prioritization during a launch cycle can often be a very big wrench in the spokes.
In a partnership with an SEO provider, or in dealing with your own SEO team, you have to remember the "fear of flying" analogy. If you're afraid of flying, simply ask your captain if he's planning to get you there safely. Chances are very likely that any partner you entered into an arrangement with, and even more so an internal SEO team, is just as concerned about ranking and performance as you are.
For a new site, the first goal should be to rank for brand and potentially some local or other modified long tail searches. Give the process time and continued attention, and rankings should be visibly rising after six months.
For redesigns, the primary first goal should be to maintain current rankings for high-traffic terms immediately post-launch. Next, establish that your optimization is in place and start working to develop trust in the new pages and understand how the search engine sees them. From this, you can either increase or decrease your expectations for incremental success over the old site.
Frank Watson Fires Back
Interesting mate -- length of time it takes to get ranked is always something you get asked, and it is a hard one to answer. Competitiveness, domain age, and brand level are the three things I look for at the start -- after that it becomes an endless endeavor.
Using existing analytics can help, but many times you're implementing them as well. One of my clients put bonus conditions on getting ranked on front page -- left him after six months, then a couple months later many of the bonus terms popped into place. They just don't get the idea of time in our industry.