I'd like to interject something here now, to help Averil out.

One thing I learned a very long time ago in genealogy, is that the only person who can vouch for an age at death or burial is the person who's dead.

If Averil is right, and the 1835 burial is the John born 1770, then he'd be only 65. That's a big difference from 87, I know. But we've seen clerks who wrote the wrong number down, or who couldn't read their own writing from their notes, or just plain couldn't remember what they were told by the time they entered it into the register. Poor John probably looked 87 when he died!

I'd like to know how all the theories would work if we replaced "87" with "65" or even "67" which at least has one digit right. I suggest giving it a try.