Have you candled the eggs while she is off to see if they're viable or still alive?
I wouldn't worry about her spending some time off them each day, that's healthy for a setting duck... some of mine only take short breaks, but my best and most experienced ones will be off for a couple to a few...
Hi there my call duck has been sitting on 10 eggs now for 26 days and nothing has come. She has freaquently been getting off the eggs for about half an hour before I get worried about the eggs and put her back in the coop. What should I do and will they hatch as she has been off them so much...