One problem we’ve had crop up on several occassions is that clients believe their content is ready until they actually see it on their website, and then ask for changes. Sometimes this is easy enough to deal with, but sometimes the changing and checking can really make things drag out.

I guess your “timeline” is where this issues is best addressed, but I also think that for any project of a reasonable size, there are going to be phases and checkpoints that need to be passed along the way. Building these checkpoints in, and getting clients to clearly sign them off is a really important if the project is going to be enjoyable and not a headache.