Avoid mineral oils on leather saddles as they soften the leather an allow it to sag. Brooks sells "Proofide" for their saddles, which is a mixture of tallow, vegetable oils, beeswax and citronella. Another good treatment is "Sno-Seal" which is basically beeswax dissolved in a solvent. The solvent allows the beeswax to penetrate deeper into the leather, and then evaporates leaving the wax behind. Whatever you use, use it sparingly. Over-treatment will shorten the life of you saddle.
As mentioned earlier, I have several Brooks saddles in use here. The newest is about 20 years old; the oldest almost 50. I only use Proofide or Sno-Seal on them and they are comfortable and holding up fine.
IDk , have a 30 year old Pro, warm [100F in oven] it absorbed a table spoon of proofide ,
Like a sponge, cool, the waxes consolidared again, and I've been riding it ever since..
so It is a YMMV situation..