Sufficient is no absolute term, it is dependent on free time and other resources. Which is another way of saying I agree. With that said there is unavoidable attrition of friends from changing circumstances, locations, schedules and other factors that get in the way. I find it optimal to spend a certain small proportion of time seeking out new experiences with new people. After all, what are the chances that the people I currently know are the most suited to me out of the tens of thousands in the surrounding area? It feels like a betrayal to think such a thought, but I can come up with no good reason why I should listen to that particular emotion.

Eventually things change and I see no reason to replace the friends who must leave my life with the first reasonably compatible people to come along, when I could instead take a proactive stance and do better. We decide the people we want in our lives