In our country also, people are suggesting that prime minister and ministers should not have more than 2 terms (10 years) and parliamentarians should be limited to 4 terms (20 years).
That seems reasonable and may work better for your country.
Interestingly, these people always win elections
I wonder why.
Knowing why, or having that gut feeling as to why, is the reason why term limits should be in place.
1. If there is a tenure, then we wont have much people coming inside the political systems since after 12 years, its a dead horse.
I would expect public servants to climb the ranks, so to speak, from City Council to Mayor to Governor to a congressional or senate seat, to then run for President.
If term limits were in place as I suggested, you could get someone fresh out of college with a political science degree who's 22 years old who sits on a City Council for 4 years, and with that experience, be able to run for Mayor by 26 (but likely stay in council, moving up in power, till the 30s), and after their mayorship is up, run for Governor at 34 (even though they can run for President at 35) to get more experience in governing. By the time they're done with their first or second term as a Governor, they should have enough experience to run as a senator or congressional representative at 42. They could then be a congressional representative for 12 years, making them 54, then either run for President or hop on over to a Senate position and be 66 by the time that ends.
If they hopped from Congress to the Senate, it would only limit them to 1 term as President (by age), but the Constitution states two terms, so that would be unlikely to change.
There are many other paths that people take too, like becoming a police officer and working their way up to Chief before running for higher office.
So, it's not necessarily a dead horse as it's a slow progression to the top over an entire career.
2. So much of corruption because there is just 12 years to make a fortune
It would likely cut down on corruption because they would need to act more swiftly to make a fortune, which is quite observable, and would likely get them voted out as it would be too obvious as to what they're doing as opposed to slowly drawing it out over 30+ years.
3. They will find reasons to stay in power through ancillary mechanism such as participation bonus, directorship, chairmanship etc.
There would also need a law in place that would prevent this. Wherein, after they leave a high office, they're unable to sit on a Board of a large corporation or be a lobbyist. It's already very similar with the US military in that after someone retires from the military, I believe they can't work for a (defense) contractor for like 6~8 months, so this would also be a very popular idea to propose if we're speaking of term limits too.