That may be in part to their 'president for life'. Leaders are not immortal though and transitions between them have seen large and sometimes catastrophic changes. China designed its modern political system to avoid that, only for Xi to undo it and purge younger potential challengers.
For life and is 71 in arguably the most stressful job in the world. The risk of mental decline cannot be ignored, particularly as he has now served longer than any US president in all of history.
Although I say that and then I went down the rabbit hole of trying to find which individual had the longest tenure of presidency and vice presidency combined. It seems like it’s either Nixon, HW Bush, or Biden.
As the US president is more or less in the same position as the monarch in the UK -- the main *official* task is to approve or reject legislation already passed by parliament -- you should perhaps look at the 63 years 216 days Victoria reigned, or 70 years 214 days of Elizabeth II, both far exceeding any recent US, Chinese, or Russian supreme leader.
I recently noticed with horror that my birth is now closer to the end of Victoria's reign in 1901 than it is to today.
