Personally, I'm considering 2 days. I think- should I fail/ pass out- hopefully by that time, I'll be well enough to cancel the email. Probably depends on whether you want to prevent anyone else finding you- but you could always put up a sign to alert the authorities in addition- should someone get there before the email sends. I don't know really, I feel like leaving the time margin too short means there's more chance we could be 'saved'. I don't know how long it takes for a corpse to start badly decomposing though. It's not really something I want to look up either- incase it's flagged and makes the authorities think I've murdered someone!