Stress
Nine months out of the year, an IRS agent's stress level pretty much amounts to getting to the office on time. Sure, there may be specific instances of tax code-induced panic when you wonder if you correctly applied law 23:11b of subsection 1272, or if you need to go back and re-work all of your numbers. Other than that, the work is predictable and, if you like numbers, rewarding.
However, during tax season, when the majority of the population turns in their tax returns at the last possible minute, things can get pretty hairy. You'll need to supervise temporary workers who often have little to no training as they go through thousands of hand-written tax forms. You'll be responsible for evaluating electronic submissions and flagging any which arouse suspicion. Tax season will be hectic and stressful, with long hours and mountains of paper work. But three months goes by quickly.