I think a minute is plenty of time for this sort of thing. Any longer and it would pretty much be freeware.
The previous commentor is so annoying to think the developers should change the nag period to suit one cheapskate.

Absolutely wonderful app. The previous version (1.0.5) was buggy, but this version is much improved! It works great, but YOU MUST READ THE DIRECTIONS or it will feel buggy and you'll just trash it after a few minutes.

While Mac apps really should NOT require you to read the instructions before using it, this one sticks so closely to David Allen's GTD system it's scary.

The trick with this app is to let it work for you. Read Getting Things Done by David Allen and read the help doc that comes with. (Don't assume something isn't working, etc. Learn to use it.) You have to resist the tempation to just drag things around. It really does the thinking and organizing for you if you let it.

I basically have three apps running all the time now. Inbox, Mail.app, a web browser, and iCal as needed. Everything else is just gravy.