For sure, the EGR is the scourge of any engine.....imagine, filthy exhaust gas being returned to the engine to be reburnt - makes little sense. However, it does reduce the volume of nitrogen dioxide produced by lowering the temperature of combustion therefore it is here to stay. Turbo or non turbo, they are all the same.
Bother can be expected at any time over around 30000 miles, depending on how the vehicle is driven and when the thing is dismantled the amount of coke and gunge build up can be staggering. They can be cleaned to a certain degree if removed from the engine - these spray cleaners don't look at it, I'm afraid.
The EGR isn't meant to be open at all times of course, that depends on engine load, temperature and speed - but if its jammed open then performance falls, naturally enough.
Some people blank the EGR off - as I have done on earlier diesels. How this affects any other sensors or indeed the MOT I'm not in a situation to judge.
Similar findings exist on turbo charger circuits....the operating valves get filthy and the amount of oil and other gunge in the intercooler pipes can be amazing - prompting the purchase of a new turbo which isn't always necessary!
John