How long should I wait before retaking an assessment to see if anything moved?

Six weeks is early for a trait measure and about right for a state one, and the difference is worth using.

State measures — stress, mood, anxiety symptoms — ask about a recent window, usually two weeks, and are designed to move. Retaking one at six weeks is reasonable and the movement means something, with the caveat that it will also reflect whatever the last fortnight was like independently of your work.

Trait measures are built to be stable, which cuts both ways: real change shows up slowly, and short-interval retests mostly capture noise plus whatever is salient today. Three months is a sensible floor, six is better. There is also a mechanical problem with retaking soon — you remember your answers, so the second take partly measures consistency with the first rather than your current state.

The thing that makes a retest actually informative is narrowing what you are looking at. A broad trait score is an average over facets, and moving one facet barely shifts the average — so a real change looks like no change. If you have been working on restarting after a broken streak, look at that facet, not at conscientiousness. Movement on the specific facet with the others holding is a much stronger result than a shifted overall score, because it is what genuine targeted change actually looks like.

One thing to do now rather than later: write down what you expect to have moved and by roughly how much, before you retake. Otherwise the result gets read to confirm whatever you already believe about whether it worked, in either direction. That prediction, written down, is the difference between a retest and a mood check.