I am wondering how to word this, and simply say that I am not wishing to be critical of anyone who wants to set themselves challenges. So please take this in the spirit in which it is intended.
Over time, people have felt that they want to travel, to do challenges and so on. However, for some reason (and I'm not quite sure why) these have ended up centred around just a few places - certain destinations which have then become wildly popular. Of course I get the idea of doing 'highest mountains' but I would suggest looking at other mountains that represent a challenge, where there will be fewer people, and you can enjoy the beauty.
I have been up some beautiful mountains in the UK & Europe, and had some wonderful experiences. I'm not going to suggest them as you have to find the ones that would best suit you (yes, I know it's your husband!)
I would say the same about almost any 'popular destination'. Look at guides and think about what you really want to see and experience.
I realise that may not 'hit the spot' for your DH!
