shutdown - Computer care: Hibernate, Sleep or Shut Down?

Which is the best for the "longevity" of your hardware, when done on a daily basis?

Should I use sleep, hibernate or shut down?

EDIT:

As evident in some of the answers, the answer seems to vary by OS and computer type.

Answer

Although I don't have any references to document it, I've heard tech pundits commenting that the industry is moving away from any kind of hard shutdown in favor of devices which just sleep or go into standby mode. Even if your computer is "completely" shut down, there's a good chance that it has wake-on-LAN or similar functions enabled by default which require it to be actively monitoring some source of input for a wakeup signal, thus preventing it from being 100% powered down. Unless you take this as evidence of some sort of conspiracy to wear components out faster so that they'll need to be replaced sooner, it seems pretty clear that the hardware manufacturers do not believe that a total shutdown is ever necessary.

My personal practices, then, are:

• 
  

  For laptops, I use sleep mode more-or-less exclusively. I close the lid when I'm done using them for the day and, when I open the lid the next morning, they're back up and running within a second or two.

  
  


• 
  

  For stationary machines, I do none of the above. I just leave them running 24/7.

  
  

The only times I reboot (hard or soft) are to switch operating systems, to install/replace hardware, or when the OS starts slowing down due to accumulated resource leakage (usually takes a couple months on OSX or the better part of a year on Linux; I don't think I've ever gotten Windows to this point without first either needing to reboot to finish installing something or being forced to reboot to recover from a game crashing).

This has not adversely affected reliability or lifespan of my hardware. On the contrary, I routinely keep machines active for 5+ years and retire them in favor of more powerful hardware well before hardware starts to fail. Exceptional cases aside (e.g., being dropped in transit, severe overheating due to the room temperature exceeding 100F), I've never had a critical hardware failure on a box under a decade old.