Up until The Bad Batch, I had assumed that the Empire shut down the cloning project but kept the clones the Republic had already paid for (to not waste resources). Meaning that new clones were not purchased after the end of the Clone Wars, but any that had would continue to be raised and trained to be soldiers until they entered the Stormtrooper Corps. If that was the route taken, the last Jango Fett clone would have entered service around 10 BBY, with those clones being the human physical equivalent of 40 year old men by the time of A New Hope. Meaning they would be still be viable soldiers, but getting older. The First Generation Clonetroopers (like Rex) would be 32 years old and be the human physical equivalent of 64 years old. This also means the Rex would look like he was in his 70s at the Battle of Endor. If Rex is still around by the time of Ahsoka, he would look like he was in his 80s, while he would actually be in his 40s. If the Empire still had some last gen Jango Fett clones (had they gone the original speculation of not wasting spent money/clones), they would be about 30 years old and look like they were about 60 years old.
Now if we take The Bad Batch into account, it is possible the Empire trained up the last groups of five year old (the young Logan looking clones) and up clones into service. If that was the case, than the last Jango Fett troopers would enter service in 15 BBY, only about four years after the end of the Clones Wars, and they would look like they would look like they are 50 years old in A New Hope.
This also means the it is entirely possible that the clone babies in the tubes that Obi-wan saw at the dawn of the Clone Wars may have been the last batch to become troopers...or were the slaughtered never to become troopers...depending on what the Empire did with the four year old clones.
