Ex-BH and myself have both had good experiences with buying aged tups. The first one he bought was a previous champion and top-priced shearling tup of the year of the breed, and was for sale at 3 years old, having improved the breeding flock at his then buyer's home but still having some great genes to pass on. (We weren't breeding pedigree Charolais but we wanted to try a Charolais tup on our Texel cross commercial ewes.) We paid as much for Perry as we would have paid for a near-the-top-price shearling tup of our usual type, but it was a great decision. We worked him for 4 years; his daughters were very easy to pick out so it was not difficult to put them to other tups, until they started to be quite a large proportion of the flock, plus we by then had some granddaughters, which weren't quite so easy to be sure of by eye.
With his stamp on the breeding ewes and the fat lambs, our grades for lambs went up by one or two points, and they matured on average 2 weeks earlier, which meant more away while prices were higher earlier in the season, and to the better-paying markets, plus we were getting a good 60% of our fat lambs into the "bonus box" (where you would get approx an extra £3/head for producing the lambs the buyer most wanted) as opposed to around 20-30% previously. (When I wax lyricial about Charolais for breeding fat lambs and commercial ewes, this is why!)
Ex-BH was very fond of Perry. Not just the impact he had had on our flock and bottom line, but he was also an utter pleasure to own; you could literally walk up to him in the field and tip him up to do his feet! When Perry finally had to go, we bought a tup lamb from the same breeder who had sold us Perry. Perry was Fred's great-grandfather, and Fred also went on to produce many fat cracking lambs for us. We didn't keep any of his daughters for the first few years, so that we could use him for longer. (Plus, we didn't want the ewes to be more than 50% Charolais on our farm with our climate. They are a thinner-skinned, less hardy animal than the Texel.)
Sorry, got a bit carried away... but that was all just to say, buying the right aged tup can be an excellent choice, and repay you what you paid for him several times over.
Perry would have worked to 6 or 7 years old, and was on what was a fairly hard farm for him, with 30-50 ewes at a time.
My own current tup was bought at 3 years old for meat price. He will be tupping for us for the 3rd time this time, and will stay here as long as he is working and fit and happy. I am keeping some daughters from last and this year, and I will be putting them back to their Dad when the time comes - but I won't keep any of their offspring for breeding back to their dad/grandfather. (And wouldn't sell any for breeding either, not that I sell breeding sheep - or indeed, any sheep - very often these days. It's a meat-and-fleece flock just for us, and tiny compared to the commercial flocks I had in the north of England.)