Creating and maintaining a site-production schedule can be a challenge. Many factors go into creating a production schedule and many are not unique to open source. But some schedule challenges are associated with open source.
When you consider the unpredictability and lack of control often experienced with open source, your ability to predict a schedule and deliver a fixed set of features becomes a juggling act. Add to the mix potential learning curves, and you can have a scheduling challenge, especially if you promised that certain features on the site would be available at certain time.
The following sections offer some insights into scheduling a Drupal project.
Assume for a moment that you have chosen a waterfall approach. You have planned all your activities and it looks like it will be 12 weeks before the site will be ready to launch. Unfortunately, you need a web presence six weeks from now because you are presenting at a conference and want to promote your site. Assuming you don't have any other factors (such as approval cycles and funding availability) influencing your decision to use a waterfall approach, you might consider a different method.
You might choose a phased approach with an agile method such as Scrum to get the ball rolling quickly. You might not get all the features you need at your conference, but you will have a web presence that you can point to while the rest of your site is completed.