Hi Everyone,
I have had the e flow for over 2 years now and yes, I boil after each use. I boil the metal part as well, I always have, that is how the distributers here in Australia explained it to me.
I rinse the parts firstly in mild soapy hot water, then I boil all parts in demineralised water for about 5 mins. To save time, I start the demineralised water to boil whilst I'm using the e flow, then when my nebs are done, the water is already on the boil and that saves me time.
The e flow is high maintainence from the cleaning aspect but, I've never had a problem with boiling the metal part or other parts of the e flow (mind you, I'm careful not to boil for too long).