Ignoring time jumps due world level quests, one year passes approximately every 24 real life days which means a character would age a little over 15 years for every real life year. Given the prevalence of healing magic among adventurers you could draw parallel between it and a higher technical knowledge of, say, medicine. People, at least people with access to healing and those with immunities to infection will likely live longer and have a better quality of health resulting in being more active even through what we term now to be middle age. This, generally, would include many adventurers.Assuming few or no great jumps in in-game time and a fairly young starting age a human character could be RP'd for four years or more. Now, at that point it might be interesting if someone could change their appearance to that of the old woman or old man..
But the use of haste magic and speed potions would cause PCs to age more quickly.