I would give this up as a bad job. The astrological methods aside, it is a fact that the average life expectancies in most countries of the world have been steadily rising. Currently in the U.S., the average life expectancy for females is 81 years; for males, it's 76 years. The old methods of death prediction developed back when few people lived past middle age, and many died of childhood diseases and injuries.
Keep in mind, moreover, that the 8th house stands for many things besides death. It also represents one's genital and eliminative organs, inheritances, "shared resources" such as investments, and the occult, among others. Any one of these topics could be uppermost in one's life during the year of a given solar return with an 8th house emphasis.
The solar return is basically a transit chart for the time when your sun returns to its natal position. The planets continue to transit throughout the year after this moment is clocked. I would encourage you to look at your previous solar return charts and to consider how much of what they augur actually came to pass in your life.
Please realize also, that many people are born with the so-called diagnostic aspects in death prediction. Just for example, I have Mars in the 6th opposing Saturn in the 12th natally. Sun-Mercury conjunctions are common, and roughly 1/12 of the human population will have an 8th house sun. My Aquarian and Pisces planets long ago progressed into the 8th house, and are still there. So am I!