If we get offered £30m or above for him, I'd sell him. You're never going to get offered more than that for him, so he's peak value, and all players are replaceable.
That's fair in terms of valuation - probably will never get more for him. However, we don't have to sell to buy anymore. I think we should only sell him if we can get a player that better fits Silva's system and improve our squad as a whole. If we can't do that then we should hold onto him until we find that player.