My goal here is to deliver this project as soon as possible, so I will only keep a certain set of features at very first. When we reach a stable and workable stage, I will start to evaluate different features and decide which of them to add. You know, there is priority to think about. For example, when you have A feature and B feature in the TODO list, A feature is awesome, you want to do it badly, however, your customers want B feature badly. I will implement B feature first.

There are many factors to think about the directions of a product, such as

 * By adding this feature, how many users can benefit?
 * By adding this feature, would anything be impacted?
 * By adding this feature, how can I do the migration?
 * How much it costs to deliver this feature?

From my perspective, 80% of users would only need these kinds of interval. And only 20% or even lesser would need arbitrary intervals. For product sense, surely I will try my best to make 80% of users happy and try to make 20% users happy later.