How long does concept art usually take you?

I’m starting a small 3D animation project on my own, and I’m trying to plan my schedule and figure out how much time I should dedicate to each stage.

Concept art I’ll be doing:
-Character design
-Environment Design
-props design

I’d love to hear about your personal experience.
How long do you usually spend on concept art before moving on to the next stage of a project?
Do you have a specific process or timeframe that you usually follow?