I have three TiVo units that are operational with a total combined operational time of 6 or 7 years. I have never put one in standby, even to see what happens. I have never had a hard drive failure in a TiVo. I also have several computer systems running 24 hours a day. Each has 2 hard drives, all spinning constantly (no green modes here). I always have at least three systems running and have for the last 10-15 years. I lost track of how many have died over those years, it is somewhere around 2. I have a shelf full of operational but obsolete drives. I had a defective batch of 16GB Western Digital drives die at work a few years ago when 16GB was hot stuff. Of 8 drives purchased, 4 failed in the first year. Of the remaining 4, 3 are still in use, one was never taken out of the box. Other than consuming 8 watts (2 watts idle) in a device that draws 40-50 watts, there is no harm in letting the hard drive run over night. You can purchase a replacement hard drive from different vendors. They come preinstalled with TiVo software for your model of TiVo and take about 30 minutes to install.