I've been emailing back and forth with another professional who has been very generous in sharing a workflow developed at their institution. This professional has gone to great lengths to answer my questions. Given that he has no obligation to answer my questions, I'm starting to feel that I'm overstepping boundaries by asking for more details that would require a higher level of investment for him to answer.
I feel that "I hope I'm not asking too much" is cliche at this point in the discussion. What would be a more sincere way to communicate that the effort is appreciated and helpful, and then follow up with another request while making it clear that he has no obligation to reply. It may also be helpful to note that this would be the last question.