Randomly walk graph, at node, remove any edges older than X time. (Maybe 60 days?) If node has no edges, remove node.
Alternately, keep an entire list of edges sorted by date. Set a max size (5 million?). When the list gets longer than that, remove all edges over the length, look at the nodes that were associated with the edges and if any of them have deg = 0, remove the node.
Randomly walk graph, at node, remove any edges older than X time. (Maybe 60 days?) If node has no edges, remove node.
Alternately, keep an entire list of edges sorted by date. Set a max size (5 million?). When the list gets longer than that, remove all edges over the length, look at the nodes that were associated with the edges and if any of them have deg = 0, remove the node.