I’ve come to think of my journal as more of a workbook/playbook/brain dump. It doesn’t have to be perfect because nothing is ever perfect anyway. So, some entries are quick and short and over within seconds. Others and long and detailed and take much more time. So, as you can see, the length of time that I write varies quite a bit. Yours can too.
How long should you write for? That’s really up to you and the time that might have available. I would recommend at least 5 minutes a day to get some of your thoughts down. That said, it is OK to not write at all. It’s OK to only write for a minute. It’s OK to write for hours. Do what feels right to you. Give yourself permission to write for however long you want. Have fun!