Read the paper and create your own thoughts on developing either before or after your read the thoughts of the reviewers.  

But do not enter your development letters online earlier than 8 days after the reviewers’ target date and 14 days later is even better.  Here is why: we expect some of our busiest and most productive reviewers to respond only after a few reminders that they missed the target date for your reviews. Once you enter your development letter into the system, the system is designed to prevent additional reviews from being submitted.

The default target dates for editors (by which the system sends reminders) is two weeks after the reviewers’ target date. Waiting between 8 and 14 days after the reviewers’ target date would be ideal.