The 3-letter search limit is pretty much standard with most forum software. This said, in term of search flexibility and usefulness you shouldn't sell yourself short: this board is head and shoulder over most others out there since on this one a user can do a fast and reliable search at the post, thread and user level. Moreover, the results are displayed in a logical and easy to use manner.
There are many boards out there, on all topics, where most of the content is essentially buried because there is no way to search efficiently for it, and this is not the case here.
M.