Excel can get cranky if you give it files containing too many (especially duplicate) objects, and this class can help to avoid those. In general, it's much better to make sure you don't duplicate the objects in your code, as this is likely to be much faster than creating lots and lots of excel objects+records, only to optimise them down to many fewer at a later stage. However, sometimes this is too hard / tricky to do, which is where the use of this class comes in.