When do you back off AK, AQ?

[PFrese]

It seems lately that my AK, AQ (suited or unsuited) are missing. Meaning no K or A on the board, no big draw, etc. Typically, I will raise these hands preflop, then bet out the flop not matter what comes. If the turn comes with no A or K, I will bet out again if checked to, and it is usually there that I get hit with a check raise or get a caller or two. River comes with another blank. I bet again, get called my some schmuk holding 22 (or whatever). My question to you guys is when to do back off AK, AQ when they miss or do you? Do you keep ramming eventhough you know that you are beat by any pair?

I know "it depends", but I am looking for any generalizations that you can offer!

Thanks!

PaulF