1. It's a non-stop task along with each stage of a project.
Even through in the Institute of Design, the school emphasizes that there is a linear process begins with User Research, and ends by Design Synthesis, my finding was research will always exist and designers couldn't stop testing the hypothesis, gaining customer feedbacks or study secondary research.
My theory is, confining user research in the first stage of the design process wastes its full capacity, and will result in disconnection between research insights and design development and implementation. For example, a design concept which completely follows the design principle informing by well-conducted primary user research doesn't mean it is an outstanding concept, nor guarantee on any financial success. As a result, design couldn't live without research, and also, if no one transforms the research insights into design, the insights would only stay on a piece of paper.