Adulthood friendships are fated to be seasonal. once the peak season is over, you guys will naturally drift apart, like the season. When its peak season, live in the moment, when its off-peak, let it go naturally. If you really treasure the friend, make sure you are low-maintenance, as no adults have time to invest 25 out of 52 sundays on you, we all have ageing parents, spouse, career, nieces, nephews.