When do you freshen up a dark stock and when do you leave it alone

[King Cobb]

I realize this has been discussed off and on over the years, but it is something I am currently considering on one of my darker guns and seeing as the forum is moving a little slowly and searching through old posts the past 4 days hasn't given me the results I was hoping for, I thought I would see what kind of discussion we could get going.

Basically for me it comes in to two seperate areas- If the stock head is significantly oil soaked than it is time to fix that. This one I feel pretty certain on. If the oil is threatening the integrity of the wood it needs to be dealt with.

the second one is a little murkier for me. If a gun still shows it's grain and character that is great, but at what point of that original finish becoming mostly dirt and oil from being handled, does it become detrimental to your enjoyment of the gun? Do you believe that an original finish no matter how dark and worn away should be left untouched even if you can't really make out the character of the wood anymore? Or do you believe that a vintage classic parker needs to have the wood in an enjoyable state to be appreciated and thereby restored or refinished?

Pics below of some stock variations I am talking about:

The 1st and 4th stock pictured are in good shape. The 1st one is a little dark but grain is still present.

The 2nd pic is more a comparison of a refinished stock and one I think is borderline on needing to be cleaned up.

The 3rd pic is another one that I think has the potential to have a lot of grain and character under it if it was cleaned up a bit.

Anyway, looking forward to the discussion!