The life of your filter can be considerably extended if you are in a hard water area by dropping it into the solution while you are descaling your kettle.
Spares for De'Longhi products, including many older products, are available from De'Longhi Spares via their website at http://www.4delonghi.co.uk/. Alternatively they can be contacted by calling 0844 557 6438.
In either case please have your model number ready when ordering, which typically can be identified on the underside of the unit.