Good thoughts there Stitch, I don't have as much experience deep cleaning leather, but if you say get aggressive, then I'll take your word for it. I'll also keep that in mind next time I need to. as for the neetsfoot oil, not everyone's cup of tea either, good idea on the alternative, also probably easier for a lot of folks to find.
Leather is remarkably tough stuff. I mean, it does a really good job holding a cow together, right? Think about the incredible abuse that a working western saddle takes... Out all day in the pouring rain, blazing sun, pounded on by some pretty heavy butts from dawn to dusk, and yet last for years and years without wearing out.... Wash it down every once in a while... give it a rub with some neatsfoot oil (I'll come back to this in a moment.) and the hardest used saddlery can last for years. Obviously there is 'leather' and there is 'leather.' The better stuff lasts longer than the garbage. Different tanning processes, different animals, different usages.... etc., etc.
You can be really rough on most veg-tanned cowhide, though. Pretty much, the only thing you can do to 'ruin' it is get it super-sopping-saturated wet, and then dry it quickly with heat, like a hair drier. And even then, you can usually bring it back to life (I'd use 'Armor-All' to do that... It's amazing stuff!) If you dry it slowly, and then give it a rub with leather conditioner, it's just about as good as new!
But to get back to neatsfoot oil... That's really a VERY good leather 'replenisher.' But it's easy to over-use it in some applications. For saddlery, I'd put it on fairly heavily with a sponge, let it sit for 10 minutes and rub it off. It will do a great job of reviving old leather, softening it, and water-protecting it. (NOT waterproofing it!) But for something like a strop, where I might be trying to put compound on it, the oils 'may' make the compound difficult to adhere. It will definitely make the leather softer, which is NOT what I want for strop leather or shoes/boots. Shoe cream, although it does have some oily bits in it, limits that very well, yet still replenishes the natural oils in the leather without softening it noticeably.
Stitchawl