30 minutes!....It seems your users got maximum execution time setting for a script.
Actually in multi-step, session data will be save after move to the next page, so you won't lose data, but in one-step, user should change the page or click on submit to not losing data.
Ask your server admin to increase max_execution_time limit from 30 minutes to 60 minutes or whatever you like.
It seems you have an escort flynax script and you know, they are young ladies! ... typing a few words and going to makeup!