Depends entirely on the school you end up in. The EdB has guidelines re the deployment of NETs but no two NETs are doing the same thing.
Is it an interview with a particular school or is it the initial interview with the EdB? If it's with a particular school ask for contact details for the current NET and email/speak to them about their workload, school culture, weekend/holiday duties, etc. If the school doesn't want to give you their contact details they're probably hiding something.
Also, check out the AllNETS website. I believe there's a list of secondary schools where people have had bad experiences in the past...
One more thing - there are some unhappy NETs out there, but like anything bad news travels faster than good news. I reckon the unhappy NETs are in the minority but it's the bad stories you hear about.