Under XP, the OS will slow down over time, and eventually get unstable, but that can take upwards of a week depending on how much you use your OS. Reboot every so often, there's no real harm in hibernating over short periods. In a laptop, most components should be built with hibernation in mind, and HDD space is cheap, so the hibernation file shouldn't be a big deal (If it is, it's 2010! Get an external HDD, 1.5TB is the best GB/$ right now, and they're pretty cheap!)

In Vista/Win7, I can't honestly reccomend shutting down unless you have a good reason.

Should I always hibernate instead of shutting down?
Is the question of "what age are you" idiomatic,common or does it sound naturally in the meaning of " how old are you "

Can we say this structure could be used for materials  as " how age is it "
