Actually I haven’t used any SMD, all of parts are through hole ( I think they are more reliable in this way), PCB has just top & button layers and soldering is done by hand. I used lot of sockets
SMD is better than through hole (less mechanical working, shorter leads).
4 layer PCB gives much more stability (noise etc) than 2 (Ground plane).
Soldering by hand is less reliable than soldering by machine.
Sockets add another possibility of failure.

In other words, if reliability is your concern - start over. Sorry, the truth may hurt.

I especially like to use this chip because it snugly fit my needs, and it is cheap if the failure rate is not considerable, can I have any rough estimate about failure rate?
I have NEVER seen a uC fail except:
during the first 6 hours of power
due to external problems (low pin driven high by other chip and such)
due to programming not done properly
due to noise (the Uc did not fail, but uC failure was reported)
due to RC reset (again not the chip, but external stimulus)

Erik