hmm interesting...
Growing up I did take speech therapy but I've never felt that I had to go back for a 'refresher' as it were. I have noticed over the years that verbally I have trouble articulating what I want to say- but I think I've always had this issue-I just do better with written (and sign when I started signing in college). The pronunciation of some words... especially blends (th, sh, etc) seems to be going a bit and that might be related to my hearing getting worse (though I think that has leveled off.. for now).
Varies from person to person I suspect... Most HOH people I know has never gone back to speech therapy- that I know of anyway. I think some may start it up again if they switch from hearing aids to the CI- can't say for sure though.