Dr. Search replies: Well, it sounds like you're doing things right, but I would discourage you from eliminating either of the methods you are using. Let me explain.
You've seen articles and presentations about the 'long tail of search', which refers to the queries which you don't get very often but which do return decent results. Less has been said about the "short head", the queries which occur frequently. In the past, we've called these the "top 200" queries, but in reality it's those queries to the left of that point where the line goes flat in your search histogram (see Figure 1). When you are handling the top queries well, you have made a significant number of your users happy.
On the other hand, Best Bets are the tool you use to handle the top queries that need good results no matter where they fall in the default result list. Sometimes your query tuning and search engine organic results place the right document at the top of the result list. But when they do not, that is where you need to insert the best document at the top of the list using result promotion or Best Bets.
Can you just abandon query tuning? Well, if you are confident that you will never get new terms or trends, go ahead and stop enhancing your query tuning: all your top queries are answering the user query. But if you ever find new terms showing up in your trend reports, it's nice to know that good overall query tuning is helping to place good document above the noise.
We hope this has been useful to you; feel free to contact Dr. Search directly if you have any follow-up or additional questions. Remember to send your enterprise search questions to Dr. Search. Every entry (with name and address) gets a free cup and a pen, and the thanks of Dr. Search and his readers.