Sometimes you'll find yourself in a situation where fortnightly retrospectives are feeling like a waste of time; the same topics are covered, no significant changes are happening to the environment, and there is a sense that the time could be better spent on other things.
Maybe you just need to stick it out and work through the barriers. Sometimes you need to bring in some innovative or fresh approaches to running retrospectives. Sometimes though, it's time to move on to something else.
Reflective learning is great, but it doesn't come in one shape only.
Before there were retrospectives there were Post Project Reviews, and before that there were After Action Reviews.
After action reviews are held after a mission is completed. If you are running three year projects you probably need to look back over the three years and learn from them, but waiting three years is a long time to go between lessons.
These days we usually work in smaller time-frames; weeks, months and quarters. At the end of each mission we have an opportunity to look back at it holistically (rather than just an abstract period of time) and reflect on how we went in the context of the business or customer goal.