I found this on another forum but I can't put the link in here so I'll see if I can quote it. My apologies to the OP of this quote for not listing their name. I'm sure they know we're all just trying to help each other.
"Get the gun case it came in and look on the left side where it gives you model-calbr-barrel-features-weight. Look down at the bottom and you will see Product with a number under it. Next is Serial# (with a number under it too) and just to the right of the serial# (in smaller numbers) are four (maybe 5) numbers. That is your M&P's Birthday. Example: One of mine is 8240. The first number is the year "8" = 2008. The next "240" are the day of the year it was made. IF you have a 5 digit number like 10240 or 11240. That 10 or 11 is the year made."
As long as it still fires I wouldn't worry about it. Mine is from '08 and from what I've read some can have strikers break from excessive dry firing.
My 9mm has about 12K rounds thru it without a problem. Just regular field strip and clean after every range trip. I detail stripped it at 10K rounds and it really wasn't very dirty so I probably won't bother again.
Scroll down this link and you will find an M&P Armorer's Manual that you can download. Good to know your pistol. page7b