Honestly, for the $8.50 the proofide cost me, it seems worth it for a purpose-made product. I don't expect I'll have to buy more for a long, long time.

Different leather treatments for different purposes. Baseball glove oil helps keep leather supple, but will soften it too much for saddle purposes (lowering the saddle's life expectancy), and does not waterproof. Sno-seal mentioned above appears to be a waterproofing agent that won't necessarily condition the leather to prevent it from drying out and cracking.

Many of the other solutions are in between. Most shoe conditioners should take care of the waterproofing and conditioning, but may soften the leather too much.

I imagine there are other brands of products that would be just as appropriate as Proofide - I would be looking mainly at treatments intended for horse saddles - but the $5 or so (every 5+ years) that I might save is not worth the research time.

As for heating, blah blah blah...my thought is that while Brooks has a vested interest in selling Proofide, they don't have much interest in giving bad maintenance advice, so I'm just going to go with the directions included with the saddle. Oil the underside once, and leave on. Oil the top side every few months and wipe off.