Yes, you can be tired from a weeks work.. If your program is a really busy one.. They tend to change their schedule to reflect the busy-ness of the program. Day shift is not a problem, but long night shifts can be brutal. You do get used to it (Circadian rhythyms adjust), especially after doing it for a few years.
RE. the accident rate.. The accident rate was very bad in the 80's and early 90's. It has changed very much since about 1996.. The statistics all date back as far as the beginning of helicopter ems, and does not reflect the very low current rate.
Be safe out there
C4