When does one know it's time to move on from a committed relationship even though it still works?No, it doesn't make sense.
If you were in a relationship that worked for you, the last thing you'd be thinking about is moving on.
Sometimes when a decision is needed, it's not possible to "know" which choice is best. So you do the best you can.
Your issue is too complex and your question too brief to think you're going to get good guidance in this forum about whether you should move on or not. In the best circumstances, you have a support network of friends, family, and maybe a good therapist/coach to help you make a good decision.
The more information you make available to your trusted friends/family/therapist, the more beneficial assistance you're likely to get.