Sorry if this has been asked before but the search doesn't show up anything obvious.
Back in the old days I bought a few of the modified ADSL faceplates from Clarity so I could basically have an unfiltered extension for my ADSL modem. Over the years I have replaced the filter a few times with one of the spares because my modem would disconnect whenever the phone rang (I don't use the 3rd ring wire internally anywhere so it wasn't this). After replacing the filter it would be OK again for a few more years.
So my question, is it known for ADSL filters to "fail" eventually? This doesn't cause any problems if so as I can just replace them. But what about the filters on the BT side? What happens if/when they fail? if at all.. and assuming they have filters on their side of course.