I see a lot of people changing institutions after they finish their PhD degrees and a few more times before they get a permanent position either in academia or in a company. However, I see much less often these changes happening during their studies (BSc, MSc and PhD). It is understandable that when you have your life organized in a given the city (and country!), are adapted to the way a certain department works, like the research line of the lab and get along well with your PI and lab mates, you just want to stay there for a while longer. Then, the PhD thesis ends up being a development of the MSc thesis, that was already a development of the BSc thesis. When you realize, you have been in the same department for 10 years (or more!) and your career has barely begun!
My story is the exact opposite. I started my BSc in University #1, did a 1-year internship in University #2, MSc in University #3 and PhD in University #4. I am finishing the second year of postdoc in University #5 and trying to get funding to move to University #6. So far, these have been good moves.
They have allowed me to build an international network of collaborators, live in different countries and meet amazing people from all sorts of cultural backgrounds. Even more than that, all these moves have forced me to always keep an open mind for different ways to live and work. I have learned that there are different ways to solve very similar problems and none of them is necessarily better than the other, although some are more suitable to specific contexts. I have also been in contact with a wider variety of issues than I would have been had I not moved so much. This has made me reflect upon topics that I would not have thought about otherwise. For instance, gender imbalance in high academic positions was not obvious to me when I was at University #1 because I had roughly equal numbers of male and female lecturers, but it became clear at University #3 and I ended up getting involved in gender issue discussions while at Universities #4 and #5. Xenophobia did not take much space in my thoughts before University #2, when I left my home country for the first time and was faced with prejudices and stereotypes due to my country of origin. Mental health in academia only called my attention at University #4, where depression, burn-outs and suicide happened closer to me than ever before.
Overall, when I reflect on how much moving has changed me, I consider it to be a good thing and encourage students to do the same at least once before the end of their PhDs or for their first postdoc. Unfortunately, some PIs do not encourage their (best) students to move as much as they should when that would the best for both sides. For the PIs, although it is comfortable to keep working with someone that they know can deliver reliable results on time, throwing the dices hiring someone completely new to them can bring a good (and often needed) new breath to the lab. This new breath might come in the shape of vibes, ideas, skills, practical and analytical tools and a different perspective.
For the student, there is always the personal growth, the knowledge and the expansion of the network of collaborations. However, I am aware of all the issues of moving (especially moving too often). For example, getting adapted to a new city/country/culture can be very challenging and it is often an exercise of tolerance to loneliness (good thing for me: made me more comfortable with being by myself and got to know myself better). More than adapting, the whole moving from a practical point of view is tiring! Finding a new house (and furnishing it), good friends and housemates, where to get the things that you like to eat and nice things to do in a new city is not easy and takes time. Finding your space in a new environment takes effort! On the other hand, it forces to let go, detach and be flexible. Being away from family is also difficult, especially when things are going wrong and all you need is a tight warm hug.
Finally, having a long lasting relationship can be a huge challenge. Most people find long distance relationships difficult to keep. Most jobs and careers outside academia do not allow big moves. Even when the partners are in academia, finding positions in the same institution/city is challenging. Having kinds adds a whole new layer of complexity to it and often that is when moving stops completely.
At the end, I always keep in mind that if I decide to stay, I should challenge myself to keep learning and doing different things, even slightly outside the lab’s expertise. This way I will still be able to contribute to the lab and bring novelty to the research line. On the other hand, if I decide to go, I always leave the door open because a good opportunity to come back in the future might present itself and I might be keen to return.