Not really, Because CO2 sinks. Make sure you bleed the oxygen out with CO2 after you put the lid on. There will be a cloud you can't see through when you pop the lid. Wait for it to dissipate. (You don't want to contaminate the beer)
I can think of several reasons not to though.
Skunk your beer if you don't get all of the oxygen out
You'll probably disturb the sediment on the bottom of the keg, clouding your beer
What will you learn?
With practice, you can get a pretty good idea of how much is left by gently lifting the keg. I did this this last weekend with my very first batch. Lifted the keg, thought "Well that must be just about empty..." I got one more pull out of it.