I had an email discussion with the wankers. September last year they wanted me to prove my mam hadn't had a television since March that year. I politely told them it didn't work that way.It's three years for me, watch out though because you have to fill in and return the 'no licence needed' form every two years to stay on the right side of the law.
Apparently it's the only law where you have to keep telling them that you're not intending to break.