HP flights DO count toward CO elite status. HP flights DO NOT count toward NW status... and in fact, hardly count for anything on NW unless you're flying to/from Asia (i.e. HP Phoenix-LA and NW LA-Tokyo). IMO, the HP partnership with CO is what gives CO an edge: say your husband flies the following:

30K with CO, 30K with NW, 20K with HP

Under NW, he would have 30K CO + 30K NW = 60K = Gold

Under CO he would have 30K CO + 30K NW + 20K HP = 80K = Platinum

Platinum always trumps a Gold... and in my experience I haven't seen much difference in being CO elite vs. NW elite on either: one given is that NW has larger FC cabins, so odds of upgrading on NW are better.

As far as if airlines change partners, yes they do, but these agreements have been long-standing, so I wouldn't expect any changes soon.

Do I like the airlines? Sure, CO, NW, and HP ahve treated me well-- probably because of the FC upgrades but I haven't had complaints. People here like to cut on HP, but I think they're ok--- and I guess your husband does too, since he's flown with them a lot. As far as CO, people here complain because CO sin't as attentive to service as they were about 2 years ago-- and I have noticed then change as well. (I've also noticed NW get better lately.) But, the CO/NW programs are still some of the best around, especially because of their policy for domestic upgrades for elites and companions.

One last comment: Go Blue!!