[teiferer]

Well, average life expectancy in the middle ages was in the low 30s or high 20s, but the child death factor does not bring the typical old person age to the 80s that we're used to from today, but into the late 50s, early 60s. That was an old person.

As for making the predicion more accurate, it's a rabbit hole you'd rather not enter. Whether you smoke or not or whether you live in a big city or not or your social class all have much higher impact than whether your IP is from Spain or Poland or Florida. Including people with the time and means to browse such website are a very select group. Not even speaking of VPNs hiding your actual geolocation. Whatever you do beyond "let's shoot at 80 for approximate time" may be making things worse.