This is not necessarily the fault of the company, but when client indecision or any other unforeseen delay causes bottlenecking/ overlapping schedules, there can be near-impossible deadlines to meet while trying to maintain such high standards. It's no small feat, and can create some mind-numbingly long hours that you may not get back.
On the other hand, the occasional lull in daily duties may also feel stressful, even if only for having to make up new tasks to complete in order to fill in mandatory timesheets.