Our brain can estimate something and learn to be better at it next time. Intuition I think is the best weapon against estimating something. The surprising fact is that we wouldn't be completely aware of all the variables it considers while coming up with estimation.
In the end it's all guessing. Planning is guessing, do it more often!
The actual question one should ask is how frequent should you estimate. At dropx.io we follow a hybrid model of kanban with scrum meetings. It took me approximately 2-3 weeks to get an intuitive way of judgement for estimating a particular feature. These days it's easy to guess, but a deductive way of estimating would be to calculate individual velocities of all the team members and then we can definitely end up with a calculated guess(estimate).