@Knipper:
Lots of recalls just for the favorite treat, every time. Once that's consistent, slowly decrease the treats per recall.
I did this for a 13 year old at my Husband's family farm. He ran free with the other dogs for as long as he wanted.
I also did this with a pup, who has the same recall at the farm. Ironically, at our home (an acreage) she has no recall…
just to add to this for 'the favorite treat', I added a whistle sound so that even to this day 5 years later, if I blow the whistle, he comes, I pay with a treat….99.98% reliable!!!! even when they are visiting Aunt Annette who gives them treats and it takes a good 3 minutes to get back home! (all three actually! since I live on 10acres unfenced and really nice neighbors)