Hogget is more a meat for the slower growing Primitive breeds like Hebridean, Shetland, Manx etc rather than something like a Suffolk which as twizzel points out tend to get fat if eaten older. Primitives grow very slowly and it is that slow growth which makes their meat so special, firm and so tender but full of flavour, as long as they are grass fed without concentrates. A Suffolk is a breed which was designed to fatten fast and to cook fast to suit the mass palate as Spring lamb. Growing Primitives on to 16 months or so and slow cooking is a way of producing a tender meat from an animal which is simply not big enough at 3 to 7 months old to slaughter for sale.
I would eat your wether at the usual age or you will be very disappointed .