Taking omeprazole 40mg per day for 6 months for duodenal ulcer how long does it take to heal?

Few weeks: A duodenal ulcer usually heals within a few weeks after treatment. Long-term treatment with higher dose proton pump inhibitors is not recommended, if possible. You should see a gastroenterologist for follow-up.

Should be healed: This should be healed - normally you would be titrated down to a different med by now if symptoms had fully resolved. If symptoms persist while on this dose of meds it may be time to consider having a repeat upper endoscopy (or first if not done prior) - consider seeing a gastroenterologist.