Something strange and slightly counterintuitive happens with a genuinely well-chosen car fragrance after a couple of weeks: you stop smelling it. Not because it faded. Because your own nose adjusted to a consistent, pleasant baseline and quietly stopped flagging it as something worth noticing.
This trips people up sometimes. A driver hangs a new scent, loves it for the first several days, and then starts wondering, around week two, whether it has already faded, simply because they cannot smell it as strongly as day one. Often the fragrance is performing exactly as intended. What has actually changed is olfactory adaptation, the well-documented tendency for the nose to stop registering a smell it has been continuously exposed to, the same reason you cannot smell your own house but a guest immediately can.
The real test is not whether you personally still notice it fresh every single time you get in. It is whether a passenger, someone whose nose has not adjusted to your specific baseline, still reacts to it. If friends or passengers are still commenting on the scent in week three, it is working, even if it has become invisible to you specifically.
This is actually the goal, not a flaw to troubleshoot. A fragrance that keeps forcing itself back into your conscious awareness every single day would eventually become genuinely tiring. One that settles into a pleasant, mostly unnoticed baseline, present enough for a passenger to catch, quiet enough for you to stop thinking about, is doing exactly what a well-built ambient fragrance is supposed to do.
If you are wondering whether it has faded, ask someone else first. Your nose adjusted. Theirs has not.