Sorry but difficult to work with 6 days intervals.
What you seem to have is a either a logic board problem or it buffers .
This would have to be verified inside the tv and usually replacement parts have to be tried.
This would call for a repair shop , nothing easy about those plasma ans you would be looking at up to $300 in repair to have this done at home.
If you need to find repair shops near you then look at the link below and enter your zip code ;
This will give you a list of NESDA member repair shops in your area.
This list may be limited though and you may find more the yellow pages or simply google "tv repairs" and the name of your town .
You could give a call to different shops in your area to get an idea of their rates , it pays to shop around but if i may be frank , considering the age of the tv and the fact that you can get a new 50" tv with all the bells and whistles for around or less than $450 ,I would think twice before investing that kind of money into this one.
I think your money would be better invested in a new tv .
Let me know if you have other questions and if not then please do not forget to rate by clicking on the star icons at the top, then click on Submit so i get paid for my time helping you .
Also note that it will not close this post , you can come back here at any time if you need further info or help .