Sorry you didn't get any advice about the new unit Tim, maybe noone here has one yet and you're breaking new ground?
To be honest,although I'm scared I may be tempting fate, my Eberspacher 4 is now 7 years old and going strong. I think the installation is very important, so if your install isn't good you may have similar issues with the new unit - I hope not! Also Ebers, but probably all these units, need to be worked hard and it's the short cycling that kills them off. So, don't fit a 5kW unit where a 4kW would do and make sure it goes off once you have hot water and a warm boat. I use mine for 1 hour at a time and listen for it dropping off load. After that, the stove is back up to speed and the day ahead stays toasty whilst the Eber sleeps it off!
Good luck with your update!