Every diffuser instruction sheet says to flip the reeds. Almost none of them say how often, so people either never do it or do it constantly.
What flipping actually does
The saturated end comes out of the bottle and the dry end goes in. The freshly exposed, fully soaked length evaporates quickly for a while — which is why a flip gives you a noticeable lift in scent for a day or so.
That lift is real. It is also oil leaving the bottle faster than it otherwise would. You aren't creating fragrance, you're spending it sooner.
A reasonable rhythm
Once a week is plenty for most rooms. Once a fortnight is fine if the scent still reads. Flip when you notice it fading, before guests, at the start of a week — not daily, and not on a schedule so rigid you're doing it while the room already smells fine.
When flipping isn't the answer
If the scent has faded and a flip does nothing, the reeds are probably clogged rather than empty. Dust and oil residue block the channels over time, and a blocked reed can't draw regardless of which way up it is. If there's still oil in the bottle but nothing rising, the reeds have reached the end of their useful life before the oil has.
The other dial
Before flipping more often, try adding a reed. More exposed surface gives a steadier increase than a flip does, without the spike-and-drop. And if a room is too strongly scented, pulling one out works better than moving the bottle somewhere silly.