In the lower weight divisions a fighter relies on speed and reflexes , when they start to go with age it shows against the backdrop of young smaller fighterslike a neon sign.. However in the heavyweight division it is more of a methodical pace , young or old. so you can age better in that division. the slip of reflexes and assets like that are not as detrimental as long as you can punch , you can hang around and still be competitive for a longer period of time !