The War of the Ring is pretty powerful a reason to pull up roots and change from farming to wayfaring. So if you're NOT going for the generational thing, that works fine.
My question is, what do the Wainriders, Easterlings, Wayfarers, and all, do to keep body and soul together? The options I can think of are herding, performing (a very tough life), or bartering. Anything else? Man, I don't know. Herding would be the securest, considering that you take your food with you on the hoof, but it also means that you need wide lands for pasturage that nobody else claims, or you run into squabbles with landowners, which I'm sure wayfarers do all the time.
Actually, this was the reason there was constant movement from Asia into Europe for so many centuries, because there was land to be had, and not so many people in the way. Such seems to be the case basically everywhere in known Middle Earth (from Rhun to Ered Luin).
As to specifics for Gondorians and Rohirrim, any mixture of ethnicities only occurs during times of extremity. Yes, a War of the Ring would be one such. Orc raids that destroy a homestead would be one way. One's lands turned into a battle field would be another (but very limited) way. One's bread winner being killed in the war might cause a woman to pick up roots and children and tag along with a passing caravan, a most desperate decision but not at all unlikely, given the context. Orc raids seem to be the raison détre, or however that phrench phrase is spelled - that most rpg'ers seem to fall back on. I'd like to see us be more creative than that. Sure, that could be the reason for one family, but let's try and think up others.
Having helped not at all and complicated matters further, I'll stop now.
