I've just received my first Mulberry bag and it is gorgeous! I have sprayed it with Collonil, but how often would I need to do this, is it a weekly/monthly job or will it be obvious when it needs reapplied? Also any other tips on keeping it looking fantastic? I can't see me putting it in the dust bag after every use. As far as my husband is concerned this bag needs to last me forever so trying to start on the right foot by looking after it properly.