Promethean have traditionally only ever provided LCD projectors with our Interactive Whiteboards (up until the release of the PRM25 DLP Projector earlier in 2009), and there are several ways in which you can extend the life of your projector, most notably outlined in this document on our knowledgebase:

There is a filter warning built into the Promethean driver. This is there to try and help reduce costs, and extend the life of your LCD projector. A lot of schools do stick to a ‘regime’ whereby they will clean the filters on their projectors regularly, but there are also a lot of schools out there who either a) don’t know about the filters at all, or b) don’t realise that without cleaning them, their projector will not perform efficiently or indeed economically!

If you are one of the schools that have a regime that is working for you, there is an option within the driver to turn this message off completely, or extend the time period between the message being shown.