If you'd like the game to continue indefinitely, you can phase out the oldest numbers as the graph would otherwise become impossible (eg by dropping 2 you can get up to 29,dropping 2 and 3 gets you to 39, etc. as high as you like)
Actually fairly confident 24 is impossible since it completes multiple K(3,3) subgraphs (unless there's some option to skip numbers or put them on a different layer)
