For me, it was 3 months. I know there are many who say that divers should chalk up a fair number of dives before they can appreciate what they'll learn in the advanced course BUT for me, in between my open and advanced courses, I had NO seawater dives at all BUT the peak performance dive took everything to a whole new level when the instructor took 2kg off my weight pockets. Usually, especially when we're on holiday or diving a new site, we're just too eager to get into the water and explore so just about no recreational diver will experiment with weighting which was why I thought the 4kg was right for me.
Had I not known that 2kg was sufficient to keep me at depth even with a near empty tank, I wouldn't have found out that I was negative in freshwater without weights and ultimately, when I had learnt better breathing control, neutral without weights in seawater too.
So to me, I was glad I did the advanced course (in a way) soon after my open water one or else I'd have wasted lots of dives being overweighted.
Had I not known that 2kg was sufficient to keep me at depth even with a near empty tank, I wouldn't have found out that I was negative in freshwater without weights and ultimately, when I had learnt better breathing control, neutral without weights in seawater too.
So to me, I was glad I did the advanced course (in a way) soon after my open water one or else I'd have wasted lots of dives being overweighted.