In my opinion (and others) yes, they're to old. De clawing is an <span style = 'background-color: #dae8f4'>Amputation</span>
, the human equivalent is losing the Finger
at the first knuckle. With older cats, it's a huge psychological change. The cat will likely become neurotic and hostile. There is a product called "soft claws", there's a post on here about it. It involves gluing a plastic sheathe onto the claws so they can't do damage but can still get about.
Also, a declawed cat will have a very high likelihood of become a biter.