At the risk of asking the obvious ... are they big enough for you?

I would also hesitate to darn socks that I intended to put any significant mileage on afterward. Never done it, but I would be afraid of chafing/blisters too. But all my SW socks have been plenty durable - though I don't have the lightest weight ones, the elastic has been wearing out long before the wool fiber.

You might darn them and use them for daily wear/sleeping, anyway...