One of the hardest things to do in veterinary medicine is keep up with all of the changes. It can be quite confusing at time, and require constant learning. My practice is currently in the midst of revising our vaccine protocols, which we did just one year ago. New data on immunizations and recommendations from specialists has changed our thinking on which vaccines to give, which ones to recommend to specific pets, and which to not give. In my 13 years in practice, I have seen numerous discussions and opinions on vaccines, and with new technology and research the viewpoints change.
This is really true of every aspect of medicine. I have seen the names of microorganisms change from what I learned in school. New technologies have become much more common, such as ultrasound and digital radiography. Manufacturers stop making certain common drugs and medications, while new ones are released. Treatments are modified as more is understood about disease processes and physiology. Whatever the aspect of the profession, there are constant changes.
These frequent changes are why we read so many journals (I'm subscribed to four) and are required to attend continuing education every year. And it certainly keeps the job from getting boring.