"Oooohh" is not the same as "Oh", and "Ahhhh" is not the same as "Ah".

I think that there's a place for prolonged vowel sounds, but when you get to exclamations that go on for fiteen and twenty letters, then you've gone off the deep end and it just looks silly.

Similarly for exclamation points. I can see the need for maybe three exclamation points for a loud scream, but going beyond that makes you look like a rank amateur.

---dr.M.