Thanks, almost exactly what I was looking for.
So the tradeoff appears to be that the the quicker I want to settle a transaction, the more expensive it is.
When you submit a transaction for the first time, it enters the client software's mempool. Miners pull transactions from the mempool if they deem the fee high enough to include. If your fee is too low, it sits in the mempool long enough that the client software purges it forever. It has to be resubmitted or it never gets mined