This usually happen on multiple HDD / partitions Machine.
e.g. HDD 1 have a OSX boot partition, and HDD 2 also have a OSX boot partition. But the user only update HDD 1's software. Then the system will realise there is some outdated applications / OS in the machine (From HDD 2) and ask you update again. No matter how many update the user do, the machine is still update the HDD 1 and cause the repeated update.
However, you are not in this case. So I will say's it's unusual.
May be try repair permission. It may fix the problem. Also, please go to check if the system really did the update properly. (e.g. iTunes is now version 11.2)