How can I tactfully ask a professor to bring requests to me earlier? I'm a PhD student. A professor that I collaborate with (not from my university) asked me on two separate occasions to help with grants that were due in a week. In both cases I managed to squeeze out 20 hours to help him, and he paid me out of his own pocket (not using grant funds).

How can I tactfully ask the professor to bring requests to me earlier in the future? I guess one way is to simply decline future requests that I cannot handle. But I want to preserve goodwill when possible - I could quote him an insane hourly rate if he again approaches me at the last minute, but some people might view that as me taking advantage of the situation, even though it's not my fault that he approached me so late. (The rumor mill can always turn white into black.) The best solution, in my opinion, is to successfully persuade him to approach me early.
Channeling JeffE, just ask him directly, as if he were human.


  I was glad to be able to help with the grant proposal.  But if something like this comes up again in the future, would it be possible for you to give me a few weeks of advance notice?  That will help me arrange my schedule to make space for the work and avoid conflicts with my own teaching / research / dissertation / etc.


However, my guess is that prior to asking you, he thought that he could handle it all by himself and wouldn't need any help from you.  He probably found at the last minute that he couldn't, and had to scramble to look for help from anyone who could give it.  So if this is how he tends to operate, such a request may not help too much.  But at least it will be a nudge in the right direction.