There is no ONE answer to these questions. It depends on your teaching style, your school's expectations and your student's needs.
We journal as often as we can in our classroom, preferably once a day. Students have composition books for journaling. We keep ours in a tub that is easily accessed. We use a spring clip to mark the page we are using. Daily prompts are given to encourage students to write and illustrate their "stories". Illustrations should match the text.
We all know the more students write, the better they become in penmanship, organizing thoughts, telling a story and expressing themselves.
The English Language Learner especially benefits from writing in English often. Those transitioning into English benefit from frequent exposure to writing in English. Practice makes everything better. Right?
I thought you might enjoy seeing some of our Journal Work from the year so far.