It all depends a lot. There are different types of fragrances, for example an eau de cologne will smell less long than an eau de parfum which will smell less long than a “real” perfume. So depending on your day and type of fragrance you might need to refresh it during the day, or not. How much you use at a time can also vary quite a bit by person and smell. People who have been using a particular fragrance for a long time tend to use more since the nose gets blind to smells pretty fast. In general I’d say less is more here. Obviously the size of the bottle makes a difference as well. Finally, a lot of fragrances will not last forever. If you keep them too long they will spoil like the food in your fridge. Usually this takes a long time though.

To give you some concrete examples, a 100ml flacon of Brioni Eclat, which is an eau de parfum, will last me about two years. I use it most days, with one or two sprays per day. A 75ml flacon of a cheap eau de cologne I liked before that lasted less than a year, because it needed more applications. The shitty Abercrombie fragrance I used as a teenager started smelling funky after about 4 years of laying in some closet.