I leave my MBP running most of the time. I had had FileVault 2 running and turned it off a week ago to test something, and decided to keep it off since it wasn't doing me much good with it running most of the time.
Last night, 556fmjoe brought to my attention, that it is possible to still make use of FileVault 2 with the Mac running, by issuing a terminal command that kills the encryption key in RAM, when the screen saver (via hot corner) is initiated. Doing this serves my needs and Mac habits much better, than relying on my MBP being off to take advantage of FileVault. I turned FileVault back on and used the following command. Now, I use the hot corner to put my display to sleep immediately when need be. Encryption is now in force, until it is unlocked again by the password.
http://www.cnet.com/news/prevent-os-x-filevault-keys-from-being-stored-in-standby-mode/
"Change the 1 to a 0 to revert the setting to its default. This will force you to enter your Filevault password when you wake it up as the encryption keys will not be in RAM and will need to be recreated."
I posted this in case others have the same or similar concerns or needs as I do.