if you do a google search on how to make linux environment variables “permanent”, you will find answers to your question. This is not unique or specific to CUDA. When you set an environment variable as you are doing, the variable is only set for the current linux shell. If you don’t know what a linux shell is, please google that. When you start a new terminal, you are starting a new shell.
So to make the environment variable “persist”, in each new shell you open, you will need a method to set it automatically in new shells. There are various ways to do it which may be specific to the kind of shell you are using. for example you might set it in your .bashrc file. This is a common question, so with a bit of searching you’ll find useful answers.