i do have the habit of working on jpg files again, so quality 12.. maybe it cannot be seen in "print", but is there a chance that there is degradation if you save in 10 versus 12?
Jpeg is "lossy" format, meaning that each time you open and re-save an image, it loses a bit. This is due to jpeg compression, so it happens at all quality levels. That's one reason I follow WHCC's advice and save the psd. (I also use lots of layers when editing, so it's handy to be able to return to those layers if I need to re-adjust an image.)