This looks interesting, but how does it deal with tasks that don't have an expected finish time? Eg, what i like about Pomodoro is that i am not planning anyth

This looks interesting, but how does it deal with tasks that don't have an expected finish time? Eg, what i like about Pomodoro is that i am not planning anything more. I simply chug away at my (hopefully micro optimized) task list, and take breaks when the Pomodoro says so. This looks nifty, but i have no clue how long most of my tasks are going to take. Limiting them to 25m or w/e seems like it would induce more stress and uncertainty. I assume i have the product slightly wrong. Thoughts?