A Workflow can take any amount of time. A Workflow generally starts executing a Task within three seconds. A simple Workflow with a single Task usually takes less then 15 seconds end-to-end.
Enabling the Workflow option for persistent storage results in a small performance impact, as the system works behind the scenes to spin up storage prior to executing any Tasks on the Workflow.
In tests, this has taken from 5 - 10 seconds of additional time.
We do not yet have customizable limits or timeouts implemented in Flow.
Yes. There are two ways this can be done