We are up to day 6 with our new JN8-48. We have had no trouble with it at all, but Im waiting for the wheels to fall off after the trouble others have had.
No the auto turn can not be adjusted to turn less frequently than 2 hourly that i am aware of. Only a small movement occurs 2 hourly, not a full 180deg turn.
On day 18 you remove the auto turner from the incubator, top up both water chanels, place eggs back into the incubator laying on their side on the plastic mesh base, shut the lid and wait untill day 22 before opening.... and you should have babies!
The auto turner would be horrible to clean if left in the incubator for hatching, chicks would get tangled up in it, and it would just be horrible!
When your JN8-48 is working as it should and turning like a champ, it is possibly worth having a 2nd incubator that is just for hatching. My first incubator was a Janoel hexabator type (60 egg manual turn) and it is a great incubator

It is very easy to clean and was about $110 off ebay with free postage (Aussie seller). I am planning to use my JN8-48 only up until day 18 and then transfer all eggs to the Janoel hexabator for the hatching process. This way I keep my JN8-48 nice and clean, and I can have the hatching incubator running perfectly temp and humidity wise when I transfer the eggs accross.
Triwuffus, I wonder if after your first hatch, if there may be an electrical person in your area who would be willing to attempt to fix your auto turner? We are very rural, but there is a little electrical repair shop a couple of towns away from us and if I ever had auto turner issues I know they would get it fixed up at a reasonable price... maybe you could find something similar in your area? I know you shouldnt have to as it should have been working from the start! But maybe it is worth looking into.
I recently bought a Brinsea Mini Eco for one of my kids, they are a good quality incubator! But we had some issues getting the temp right and in the end hubby decided to pull the thing apart

I was horrified and felt that it was stuffed for sure and we hadnt even used it. It turned out that there was a cracked solder (sp?) and hubby fixed it no probs and now the incubator works the best of all the incubators, lol. So that is why I wonder if the broken auto turner could be a real simple fix it job for the right person who can recognise the issue?
Just for fun I thought I would let you know that my hubby made an incubator from an old Esky. Our first esky hatch are due on the 3rd September and I cant wait. The Esky holds 48 eggs, here is the link he used to get the basic idea
http://www.youtube.com/watch?v=beUGfdq8ey8