Welcome to the community @fermoz! If you rename the label, nothing should affect your dataset. But if you rename the variable name you should be creating a new variable. For clear understanding please have a look at the image shared below:
Here, Age is the variable with the first deployment. I deployed it and then started collecting data. Submitted some data in the server and then had to rename the variable. So what i did was i renamed the variable Age to Age_1. Then redeployed it and then again submitted some data in the server. I then made a check on how my data is residing.
So basically, you should not lose your data even if you rename the variables. They get settled in a different variable. However, please be cautious while renaming a variable as it is always good to have a different variable in the survey form then to rename the variable. Besides, if you rename a variable within a repeat group question, you should also not be able to download your dataset. Hence, please be cautious while renaming and making redeployments.
