In Google App Engine requests have a hard lifetime of 60 seconds and any request that hits this limit is immediately killed without warning. Unfortunately, this means that people with many projects may not be able to export them all in one go because the time to export all projects is linear in the number of projects. There are also memory constraints, e.g., if you have 30 projects x 30 MB each that's almost 1 GB of projects, which is more memory than a single App Engine process is allocated.