Bob, there is not the slightest doubt that the tractor reviews suffer from a selection bias (people who are either thrilled or infuriated by their new purchase are more likely to post than neutral observers with a balanced pro/con perspective) and as you correctly point out, that the reviews are mostly done by new owners. Those factors undermine the usefulness of that section. However, so long as one appreciates these biases and limitations, it is useful to allow new owners to indicate whether their new purchase met their expectations and if not why not. It allows potential buyers to become aware of some factors that might not be at the front of the line in their purchasing decisions as influenced only by sales people and marketing literature.
While it would undoubtedly be better to have some experienced owners available for extended on line chats with prospective buyers, that would likely get old soon for the long term owners. The available alternative is for a prospective buyer to post a "what do you think of the following tractor" type post in the Buying/Pricing/Comparisons section. Having read hundreds of those posts I come away thinking that the answers invariably seem to 1) promote the responders own or favorite tractor, 2) denigrate some other choice for sometimes good and sometimes just picky or obscure rationales, 3) are likely superficial "you gotta try out the new suspension seat on model X", 4) devolve into how much horsepower or what frame size arguments amongst the different responders to the initial post, 5) a variety of other off topic discussions are generated and 6) the poor initial poster probably never got the full answer to his/her question. Sifting through reviews at least permits the reader to see someones uninterupted summary of their initial experience.
I think the review section could be much better than it is now. If more people, like yourself, posted updates on their own personal tractor periodically in an experienced user review section, you could at least overcome the newbie review bias. It would also give a longer term perspective on life with your tractor and be more like the car magazines that do extended drive tests with periodic reports. How about a 1 year of ownership minimum prior to posting in a new section called "Long term reviews"? The standard would be that only owners who had a year of experience on the tractor in question (or perhaps 100 or 200 hours) would have their posts accepted.
That the review section is less useful than it should be is not something I would disagree with but I do think there is a place on TBN for a compendium of thoughtful longer term owner reviews that openly discuss the pros and cons of various tractors.