[bob1029]

By virtue of having a queue of PRs that need to test & merge, you could pipeline this thing out pretty substantially.

The implication here being that a queue must be processed in-order, so you will ultimately have a perfect sequence of future commits to speculate against, and can incrementally build up each hypothetical future master state for a test build on one of any number of parallel build agents. As the queue depth grows, you would see higher and higher throughput.