[morzh]

Well, a new is supposedly better than old.
I mostly talk about large caps, not those interstage coupling 10uF types.

In fact Western electric old caps from 40s after being reform often times have better leakage current than new caps. I read of it, and did one (I have it in my Western Electric oscillator) - it indeed has a leakage order of magnitude below the formula that comes with todays caps.
Also if the old caps take longer time to reform, the newer ones will probably take less time.

Besides, we do know where the old caps were made and where the new ones are made today.
Somehow when I see a WE cap I do not have it in me to gut it unless it is dry.

Again, it is time and effort vs cost. If it is a buck a piece...sure.