Probably did around 40k miles split between my i3 ownership of 2 cars both were REx, never had any significant issues, the 'puter automatically runs the range extender engine for a warm up / test cycle every few weeks if you don't use it anyway
It was very useful to be able to fall back on the REx on long runs without worrying too much if the charge point was broken down on your planned mid route stop, (sadly happens a lot) the only real sphincter test I had was blasting back from London up the motorway, we'd just passed a services with 5 miles range left and the REx failed to ignite
But you know how to look after your cars Jon!
When I first saw one on the road I wasn't keen on the shape/style, but it has grown on me over the last couple of years.
Most amusing bit was on my way back from friends in Somerset in the 4/4 via a nice x-country route. One crossed my path at a small roundabout,
with both occupants in the front waving and grinning at the Morgan 
