Ask 20 pilots and you'll get 21 different answers.
- can't answer the first one as I've retired
- police 12-hour night shifts, 5 on 5 off, meant that you were ready for the sleep day when it rolled around. However, by the end of the days-off I was ready to get back to doing the job I loved. Same with time off when I was on HEMS, but night shifts were only just starting as I retired.
- it might not have been a 'novelty' factor by the end, but the fascination of the task and the amazing people I worked with (never, ever encountered a work ethic like it..) meant that I deeply regretted enforced retirement at age 60
- there can be a form of torpor that sets in toward the end of a long shift, but keeping yourself occupied (cleaning the aircraft, going over your training notes, helping out the medics with moulage and 'what-ifs?' meant that I was never bored. Occasionally under-aroused, to use the flight safety expression, but never bored.