Martin has nothing to learn in AAA. He has already dominated in AAA. I don't see how you can say he needs more time in AAA when you factor in his age and performance. Plus, he has been very good as a starter with the Nats. Let him learn in the big leagues. If you keep sending him down, how is he going to learn how to get big league hitters out?
The idea that Lannan doesn't have the durability to be a 6 inning pitcher is ridiculous. He was a 6 IP in his first 2 seasons then had a 6.3 IP season last year. The fact that you think the problem with him is durability tells me that you are way off on all of your assessments. The reason he didn't go 6 IP this year was because he sucked at getting hitters out, not his durability.
As far as Lannan goes, I'm not talking about durability physically. He has consistently throughout his career, and it's gotten worse as time goes on, been able to get the order out the first time through and the second and third falls apart. I don't believe it's a physical issue, but he is not "durable". Meaning he is not able to last, consistently, for a duration without degradation. Now if it's a mental durability, or simply the opposing team able to make significant adjustments after seeing him once, I have no idea. But he is not a six inning pitcher, as a majority of his meltdowns come after he's gone through the lineup once. Don't get me wrong, he's had first inning meltdowns too, but his main problem is the order the second or third time.
As far as Martin, he's a capable #4 right now. I think you put him in a less pressure intense situation where the focus is on learning and he's facing far less talent, thus can throw some of his pitches which are sub-par to work on without worry, he could be a #3 easily. Batters are hitting .287 off of him, he's had a couple rocky games. He had a long time in the minor leagues, and he needed a promotion to the majors to see how his stuff fared against major league talent. I'm just saying now that they see where a couple of his holes are, send him back for a very short time to polish them off. He is capable of more than a #4 pitcher. Don't keep him up here for good just because he is performing like an "average pitcher."
This is the entire problem with this team. Because our farm system was so decimated, and then the team so bad, we have accepted a culture of bringing guys far too quickly. Then when they perform at an average level, we embrace that as being acceptable, all the while forgetting that many of them could be capable of being a #2 or 3, 3.5-4 ERA pitcher instead of #4 or 5, 4-5.5 ERA guy with just a little more time in AAA. If Lannan isn't proof of that, I don't know what is. Or Martis. Or soon to be Detwiler. Not every pitcher is Strasburg or Storen, well polished out of college. Martin would absolutely benefit with another 3 months in AAA.