Short answer
There is no scientifically fixed number of days or visits after which customers associate a scent with a brand. Associative learning arises through repeated pairing between the scent and the brand experience, and differs per person and context.
Recognition is not a timer
Marketing loves clear numbers, but scent association doesn't work according to a universal formula such as "after three visits".
Someone who has one intense, emotionally positive hotel experience may remember a scent quickly. Another visitor barely consciously notices the same scent and only develops recognition after several visits.
Four factors are important
Repetition: the more often the same scent returns in the same brand context, the more opportunities there are for associative learning.
Distinctiveness: a generic scent that someone encounters everywhere is harder to link exclusively to one brand than a recognisable composition.
Consistency: when the scent is different every time, the link becomes weaker.
Emotional context: memories are formed not just by scent, but by the overall experience. Service, environment and occasion all count.
So should you never switch?
Not necessarily. A resort, for example, can use seasonal zones or different scents per function. But when brand recognition is the goal, there must remain a clear olfactory logic.
One option is a fixed base scent with controlled variations. Another is one signature scent in the most important brand zone, such as the lobby or entrance.
Measure recognition separately
If scent recognition is a goal, then after a longer period don't just ask whether people find the scent pleasant. Also test whether returning visitors recognise the scent without the brand name and which associations come up spontaneously.
Consistency over intensity
A brand doesn't need to turn up its scent to be remembered faster. Overdosing can actually create negative attention. Repetition in a positive, coherent context is a more sustainable strategy.