Oh I'd definately be questioning my assumptions well before the 1000th head. Taking a good hard look at the coin, questioning my memory, and whatever else. As Sherlock Holmes most definately didn't say but probably should have, "When all possibilities have been eliminated, the answer most probably is something you simply haven't thought of". I don't think I'd be privileging any flawed theories of anthropic evidence and embracing the idea quantum suicide for fun and/or profit until I'd eliminated a fair few other options though.