The noble republic election cycle is 8 years, which is plenty enough, provided you don't annex vassals (often), to keep the same guy around for three election cycles, giving you a nice 6/3/3 (in any combination) leader for 8 years.
With 3 election cycles and no annexations, you lose 2 tradition per re-election.
Provided you make a "gap" of one ruler in-between to get the tradition up to 100, that's a total of:
starting rulers 1+1+4*2 for 16 years = 2304 MPs
one cycle of 2+2+5 for 8 years = 864 MPs
one cycle of 3+3+6 for 8 years. = 1152 MPs
Total of 4320 for = 11.25 monarch points per month, or a permanent 4/4/3 ruler when you take everything into consideration.
Plus, you can plan your monarch skills to get the decisions that require high monarch skills.
No interregnum.
No stab hit when leader dies.
No getting under a nation in a PU.
No random "no heir" or low legitimacy.
No tradition loss on change of government type to Noble Republic.
Permanent 11 monarch points per month.
We were discussing a buff to republics?
Edit: Some republics like Novgorod and Italian minors have it even easier, they can keep the same guy around permanently, as they get extra +0.5 tradition annually.
The only downside to Noble republic is that they should refrain themselves from annexing vassals (or vassals in general), as, except in case of extremely large vassals (like, say, Byzantium reclaimed), the MP loss is worse than coring costs.