Its not based on years. It's by quota.
Most of the time they hire E5 or E6 to do the work la.
M1 and M2 is reserved for long timers.

Many worked for like 10 years still not promoted.
Then they just order you here and there to do this and that.

Those new hire M1 and M2 has no power. It's controlled by the division.
Alot of senior managers all sabotage each other.

Like how one senior manager can hire 5 people under him cause he have connection with the boss.
Then how one new senior manager can only hire 1 cause no budget. Then end up the E6 do all the work