the theory about 90 days or 120 days or whatever is to find the right "Costa Rica" for you. That includes the town, culture, climate, location (beach, mountains, city) and many other factors. Costa Rica is Costa Rica is true to a point, but there are many micro-factors that can determine where you want to live and can be happy.
Never, never buy until you stay here for a year, maybe two. You have to find the right spot for you and then see if this culture is compatible with you. It ain't for everyone.
Lastly, my experience (and I have heard it from many) is that mongering becomes much less important the longer you are here. You phuck a lot

but have a few favoritas to call on, maybe you get into a relationship.