I counted the age deaths in 50-100..950-100 range and your estimate of 650-900 hours was way too high. The # of age deaths peaked in the hour range of 500-550. Personally, I'd recommend using range of 400-700 hours as an estimate as it is closer to the truth and the approximately 74% of age deaths happen in those hours. Approximately 9% of age deaths took place after these hours and 17% before these hours. Necromancers are included in the data. Two characters got accidentally recorded twice in the data (the data totals 136 age dead characters from Graveyard in Dio's).

Graphical display of the data:

>

""

It might also be worth mentioning (dunno if it is) that only 1% of character permadeaths are age deaths, 5% con deaths and the rest deletions because the player wanted to play some other character instead.