There really is no argument among us in terms of SSD over spinner, 10 over..., or where we would stop repairing a particular device. Details may differ between us, but we all would have replaced the device in question.
On parts such as MB's, buying new for such an aged device is highly unlikely. However, on parts such as drives & memory I won't install used as long as new is available. If either of those are no longer available, then I'm more likely to refuse to work on it for residential break/fix customers. In this case, new is available so that's what the customer will get. No used parts unless there are none available. Then, if it's that old there better be a good reason why they're insisting on keeping it.
When I am unable to convince a customer of a particular course of action I remind myself that it's my job to serve their (reasonable) wishes to the best of my ability. My rates are sufficient to make the labor worth my while.