I'm a bit disappointed, but I based my time-line on how fast it took my supervisor to read my drafts with paper #1. Unfortunately, this time it has taken him longer to read and comment on each draft (although he has made far fewer comments/suggestions this time).
I gave him draft #3 on Tuesday, and he gave it back on Friday - there is minimal work left to do (just clarifying some small parts). So, my new deadline of April 1st is not likely going to happen :( I will be able to make all of the corrections by then, but - assuming supervisor is happy with draft #4 - we need to get our collaborators to read it before we submit.
I still feel ahead of the game on my thesis time-line: instead of just working on this paper, I've managed to reduce the data for project #3 and write half my thesis intro. So, I should have no problems reaching my August 1st deadline to submit the thesis!
I have a meeting with my advisory committee on April 7th, and I plan to impress the crap out of them with my progress!