I constantly need to repair permissions, hundreds need repairing weekly

Hi, this is not a new problem with my MacBook Pro, and I have recently encounter the same problem whilst trying to fix a friends MacBook Pro after she approached me with the same issue. I have had a mac in new form or another since 1994 so without being a certified Mac technician, I know my way around pretty well. I use my mac all day every day and am always on grand to help my friends with theirs so I'm totally baffled by this issue.

Each week I have to repair my permissions, in fact if I use it more that usual then it will be a disk utility fix in 2 or 3 days, the permissions that need to be fixd vary depending on what programmes I have been using, itunes comes up more than most. After a few months of this I decided that the hard drive must bat fault so, having the old one still in warranty, brought a new one, backed it up and returned the old one to the store hoping to get a refund, they tested it and found no fault with the drive... So I reformatted it and cleaned it and have had no problems with it since it's in a hard case and used as an external. Again after a few weeks I have the same permissions problem back again on the new drive... So I diced to update the operating system, now running 10.8.5, it's made no difference. I still have fix my permissions every couple of days as it get he dreaded rainbow wheel and my work flow becomes impossible. So my fiend came to me with her MacBook Pro, I much newer model than men and told me of the dreaded spinning wheel . I fixed her permissions and then again in a few days time the spinning wheel was back. I changed her hard drive too and the problem persisted the same as my own.

Please can someone help me figure this out ... Why am I getting these constant permission issues

I have downloaded disk warrior and put both macs through the software,

Is anyone else having these problems...

Sorry for the long winded explanation. Thanks for taking the time to read it.

:-)