I was just wondering how often the lamp should be changed. I have been changing it every 6 months as this is what i had read to do but in the mean time i have read that you only need to change it every 12 months of use, i was just wondering how often other people changed theirs? Obviously i realise it depends on how often my tort gets outside, if i am lucky i will be able to get him outside for 3 months out of 12 but again that is unlikely with the uk weather.