The boxes I have are all self built and I rarely upgrade the cpu and motherboards. One mobo is 5 years old and another almost 4. I've never had a battery fail and wonder how long I can expect one to last. I realise there are lots of factors involved, but am curious about the experiences of others. I don't leave my machines on permanently and generally switch on/off three times a day and have each off for a total of 18 hours. John.