I would also contend that for a large fraction of those people who have deathbed wishes, if a magic force suddenly granted that person 50 more years of healthy

I would also contend that for a large fraction of those people who have deathbed wishes, if a magic force suddenly granted that person 50 more years of healthy life, they'd go back to doing what they had "regretted". The guy who regrets working too hard at the end of life might be reflecting on some projects he put too much effort into, thinking he should have relaxed instead. Yet with 50 more years, he might get a jump on a dozen more projects, or reach for that next promotion.