Generally there is no exact answer however its best to not turn the laptop off and back
on a lot if it can be avoided. Shutting down the computer also uses power so for short
periods (many hours) using Sleep or better Hibernate would save power. Also allowing
electronices to cool and heat frequently is not the best for their long term use and
Using the Power Plans properly along with good Sleep and Hibernation settings, which
are dependent on how you use the computer, will get the best performance and lifespan
however there are no exact answers. Those which seem to be best for how you use the
system will probably also be best in the long run. If you "could" set with the magic settings
that would optimize the machines functions and life but then use the machine in a different
pattern, which we all would, then in fact you would actually get less use and lifespan than
setting to your use patterns.
One thing that many forget is that turning the screen off can also save power when you
will be away a short while and would not want to turn the computer off. This will save
some power over using a screensaver but can be hard to remember and does not save
Best to refer to your System maker's Support, their on-line documentation, and their
forums about your model.