Nozzle blocking

Can anyone tell me what the cleaning regime should be for the nozzle. I have had constant problems from day 1 with quality of prints. I have now bought some cleaning filament and run that through and it seemed to be clear. Last night I set it running on a 10 hour print and approximately 8 hours in the nozzle blocked completely.
Also is it ok to update the repetier software? I seem to remember reading in the assembly and set up instructions that I should use version 0.84 as there were still issues with versions above this. Are there any advantages to upgrading?

What filament do you use? PLA? ABS? Brand? What temp?
Are you sure the nozzle blocks? Can be that only the hobbed bolt looses grip or grindsinto the filament.

I use Repetier 1.5.6 for about 2 moths now.
I also used previous versions without any noticed issues.
What upgrading will give you is :
The way faster curaengine and the very fine tunable (bit overkill) skeinforge as slicer options.

I am using PLA at a temperature of 200.

200°c should normally be enough for the stock hotend and PLA.

What could be is, if the part has many small areas and many retraction, (slow extrusion speed)
that the filament can get molten inside the PTFE tube due to rising heat.
Then it helps to put a fan on it, to cool the PTFE tube.

You could try printing at 190C
That seems to have helped mine.

You should MEASURE your nozzle temperature so you know what temperature you’re actually getting.

My K8200 read 20 degrees high on the extruder until I created a new thermistor table.