When could you say you where through menopause? after not having a period for a full 12 months? or is it longer?

Pretty much yes: Usually you start the perimenopause with missing every other period and then you might not have a period for a few months and then suddenly spot but if it's already been 12 months and no period, you're probably menopausal. However, if you're only 45 years, you are a bit young to go into menopause and might want to see your doctor for a hormonal check to confirm.