Well I'm already at the 'prime' of my fifties (and unfortunately the second prime in the series 53, 59) so I'll reluctantly have to throw in the towel. May someone less chronologically challenged than myself enjoy it (and not forget where they parked it).
Well the next prime is not so far off, 61.
Don't give up though. I bought my Plus 4 as a 65th birthday present to myself and I usually remember where I have parked it.