Vowel length

In the first few lessons, I'm noticing that to imitate Maria DiLorenzi's pronunciation, I'm having to hold the vowels, especially in the middle of words, longer than I naturally would. I don't know if this is a reflection of Italian vs. English or of Italian vs. my speech pattern in English, but there it is. I assume, of course, that Maria wouldn't be the presenter if she didn't speak correct standard Italian! :) Of course I want my Italian pronunciation to be as good as possible, but how important is it that I nail this aspect? I ask partly because in some languages (Japanese and Hungarian come to mind), vowel length is important. I just took advantage of the New Year promotion, and I look forward to learning Italian!