I think when people vote for a candidate, like US Senator, or President, they are voting for a whole team, not just one person. Candidates, at the national level, have staffs that come with them and the issues that the candidates stand for matter.
People often do have questions about the health and / or age of a candidate. These concerns came to light during the recent Senate debate in Pennsylvania. Similar questions come up about Joe Biden's age; if he were to decide to run again in 2024.
Again, I tend to vote for the team and the issues the candidate stands for. If the candidate becomes disabled, while in office, government does continue. It's not necessarily just about one person.
This discussion came up during President Regan's term in office. He was said to have dozed off in meetings. Folks thought he was suffering from Alzheimer's disease while in office. At one point, I even remember a commentator calling him "President Prune Face."
National politicians do have whole teams of staff behind them and I think the issues they stand for are what's most important.
Age and health are undoubtedly political liabilities on the campaign trail, but I would still vote for the candidate that came closest to representing my views anyway. If not in the primary, do to the concern about who is electable, but at least in the general election.