Where I live if a landlord doesn't return a damage deposit, the tenant can go after him for double the value. From a pragmatic view, must/should the tenant warn the landlord before the 15 days are up? Or can they spring this on the landlord?
As a courtesy, you may give a reminder to the landlord with appropriate citation of BC law, but you are not required to do so. §38(1) says what the landlord must do, and §36(6)(b) compels him to pay double the deposit for failure to refund in time (noting that "in time" is based on the later of the end of the tenancy and you providing a forwarding address in writing). No section demands that the tenant provide the landlord with a warning. You may, however, have to apply to the director under part 5 to get your deposit.