If your ancestor's ages are inconsistent consider that he (or she) may have looked older than he actually was. It may be that he provided his age for certain records and the censustaker or records clerk guessed his age for others.
That's one reason ages may be inconsistent--the informants may be different and one informant may have been better informed than another.
Your ancestor may have known exactly how old he was--it could be that others who did not know his age were providing information on him.
Even when he was alive.