You pretty much have the right idea. What you need to do if you go this route is have a sample selection of your users estimate the time it took to fill out the forms, and take a reasonable average and triple it. So if took the average user 15 minutes to do it, don't delete the entry for at least 45 minutes. Make sure to test this with remote users from a variety of connection types, and with users that have not filled out that form before, so that you get a good average. Of course, this time also could be a factor as determined by how many hits you get; if you expect that only one person a day will fill out a form, you probably can clear the database on a weekly basis. If, on the other hand, you get 100 people a minute filling the form, then yes, you want to minimize the time between database clearing.