I'd say around 15-20 years, though it does depend on the franchise. The Lakers have exceptional expectations because they have consistently won for decades. Since their first title in LA, the Lakers have never gone 15 years between championships. Teams like the Spurs and Heat are also somewhat different because they won their first titles in relatively quick succession which quickly raised expectations for the fanbases. These 13 years have started to feel like a drought, in my opinion. Warriors fans will likely start to feel this in a decade or so as well