Limited synapses.

When I try to recall memories or facts about the past on command, just sitting here trying to remember, nothing comes? Why? Yet when I'm out and about and someone mentions something vague or I see something, something just clicks in my mind and a certain memory will come rushing back. Weird, huh? In 5 years, would they still come back or will they completely vanish? Did I really forget them or did I suppress them to such an extent that it's locked far way in the back that can only be triggered by pieces of the past? The brain is truly an exceptional construction of neurons.