I once had a byz prince with 15 in valour, thats the highest i ever seen, and he was 7 or 8 star gen cant remember.

i got one hobilar up to 10 in valour when he was attacking, then he got 8 stars and he was v0 when i started to use him with 1 star

and recently i got a viking berserker up to 9 in valour with a 8 star gen

but other then those times i have problem to get high valour on my units getting more 3-4 in valour, even if i put vets with vets.