In Windows 7, is there any reason to "turn off hard disk after" some time period with an SSD (that's under Power Options)? I just realized I had it set for 20 minutes, but I can't really see why I shouldn't set it to "Never" now that I have an SSD.
I think the opposite is true. Since I have an SSD, I send my HDDs to sleep after 15 minutes. They only hold my data now, no OS or programs and thus are not accessed by windows randomly and woken up. It saves a little power but mostly reduces noise.
It sounds like you have an SSD for the OS and rotating disks for data. I have ONLY the SSD. So, HDD noise isn't a factor. The only thing I can think of is the power consumption. But, I don't know what the SSD's power consumption is at "idle" vs it's being "off." According to this:
the SSD uses 150 mW when active and 75 mW when idle. I have no idea what Windows means by "turn off hard disk..." when referring to an SSD (i.e., does it draw any power at all or is it just the idle power draw). Regardless, assuming I'm doing this right, 75 mW x 24 hrs/day * $0.10/wH * 10^-3 w/mw = $0.18/day if I left the thing idling all the time (a whopping $0.36/day if active all day).