I have always used dubbin on my boots, and neatsfoot oil on my leathers.
Never had any problems with stitching rotting out or anything else.
I know that there are much "better" products out there but how much is snake oil, and how much is actually better than "traditional" treatments?
My current boots have not yet let in any water - they are made by Doc Martin and were actually advertised as waterproof, and they really are.
My leather jacket is made by Armr and is around 3 years old now and still as supple as the day I bought it, but showing signs of wear.
Leather trousers are some ageing Frank Thomas ones but are lasting very well.
My waterproofs are a 2 piece Oxford suit and has been 100% waterproof to date - about 4 years old.
My gear suits what I want to do, and I only tend to replace stuff when it wears out, leaks, or (the usual problem we all have) shrinks......