Yesterday Otto von Habsburg died. He was the son and heir of the last Emperor of Austria and had been the pretender to the thrones of Austria and Hungary (and Croatia and Bohemia) since 1922. Previously he had been the heir since 1916,
It seems incredible that until yesterday a First World War heir was still alive. A reminder both that people are living longer and longer and that the war was more recently than many think.
His long tenure as pretender to the throne is, I think, the record. Pretenders "reigning" longer than actual monarchs is not so unusual - the Jacobite Old Pretender had a reign in pretence for over sixty-four years, even longer then Queen Victoria's reign.
Of course actually being on the throne for a long time is a very different thing from being the person who "should" be on the throne, if that throne is even still around.