Google now has increased the average number of words for search box automatically. The box length goes to expand up, once you enter a longer query in a Google search box. Previously, by entering long queries, Google would notice that it's difficult to edit them because Google optimized the size of the box for short queries. But now you can search for longer queries and Google adjusts the search box's size after you perform a search.
Google query was 4 at the end of 2007, but now the average number of words you can enter is to 32 words, even though most of users don't need so mush long queries.