IOTA is a Tangle[1], which is coordinated[2] flow, similar to a Directed Acyclic Graph[3]. I'm not sure what you mean when you say "overrun nodes" but by virtue of how the network operates, this should not be an issue unless everyone is sticking with only the default nodes in their configuration, but that delves into a conversation of programmer vs user error that isn't pertinent to this thread. Some of us choose to run full nodes without incurring any speed loss, and it doesn't seem to be much of an issue of not having enough of them, only that people aren't using them. Even still, this has not degraded network performance.
[1] - https://iota.org/IOTA_Whitepaper.pdf
[2] - https://www.reddit.com/r/Iota/comments/792d6c/eli5_the_coord...
[3] - https://stackoverflow.com/questions/2283757/can-someone-expl...