It`s hard to give a precise answer as to how long it will last as it`s down to individual situations.....glue generally `lasts`as you apply it thinly [that`s paramount] and even if applying a few coats, it`s always applied thinly, and even a small bottle will not be gone within the first month or anything..... I reckon that new wearers should get the smallest sizes initially and see how you get on ...you may not get any irritation issues initially, but maybe after 2 or 3 weeks it may manifest itself, meaning you`re going to have to try a different product and for that reason I`d advise you against buying in a whole year`s supply of any product, as you may not be able to carry on using a particular one and end up with a load of it in your supplies cabinet which you cannot use...... Paul.