I have 32k miles on my Prinz system with Flashlube, i had to change my plugs from the standard ones though as it started misfiring almost as soon as i had the conversion done. No problems since the new plugs.
I think cars that do long motorway distances are more likely to be affected because they have a relatively short time running on Petrol, if your only doing 30 miles then the first mile is Petrol anyway.
Daniel.