Everlong, the one guy on that list that I think they could have legitimately extended to a long term deal would have been Graham, but even his case is questionable because of his injuries in the past. Branch never proved himself worthy of a huge extension, and signing him to one while there was little cap space, and there were concerns over his health and production would have been shortsighted. They did try to extend him (he wasn't a free agent), and they tried to do so at a time when he proved his value and showed he could stay healthy. Samuel, with the exception of this past year, never showed he was anything more than a serviceable starter, or a competent nickel. Hell, in '05 he didn't even have a very good year.
I think they could have been wise to extend Givens before '05, but I don't know of many other cases where the cost of an extension represented value, or did much to improve the team long down the road.
Ty Warren, someone who has shown that he is an excellent starter and durable, is a potential target of an extension. They know what they are doing, and it is much easier for us to sit here after the fact and say "well, they shoulda done this..."
Hindsight is 20/20, of course.