Yeah, it seems to Pete; I've never had a wet foot with my Altbergs, now on my third pair. I'm wearing non-GTX ones at the moment and have been walking in the wet woodlands with these on for four weeks now, average about twelve miles a day so mine don't get much chance of a proper dry-out either, but I Ledergris 'em every other day and I've stayed dry so far.
I reckon you wouldn't go far wrong using the Nikwax products from the waterproofing point of view, but my problem has always been cracking of the leather behind the toe-box and the Ledergris seems to be the answer (for me) to that.
I'm anal with my kit too mate, *I only buy the best I can get to do the job I need and I don't see the point of not putting the time and effort into looking after stuff; very much like tools, which I suppose is what they are.......