Multi-Step Form Data Storing

I have a rather large mobile form that i've split up into 6 steps.  It's been a while since i've created a wizard type flow process, and wondered what is the best practice way to set this up these days?   The biggest question is on how to store the data between steps.  The form itself should be easy enough to go through and fill out in one sitting in probably 5 mins or so.  I don't want to provide a mechanism for a user to only complete a partial form and come back later.

So my question is do I store the data in the session as they progress through the steps, then save it all to the database at the end?  This seems to be the way to go versus saving to database after each step, but just wondering if that's a best practice in this situation.

Thanks!