Would the US political system work better in terms of stability & continuity if they allowed a maximum of 3-4 terms in office instead of 2 ?

No, it would not work better. If you want proof, just look at Congress, both The House of Representatives and The Senate. There are more old fossils, (Democrat and Republican) that are as, if not more brain dead than Joe Biden.

Instead of allowing more term for The President, this nation needs to establish term limits for Congress. The Founding Fathers never intended Congress to be career by people who could not and did not succeed in The Private Sector. 

You know I don’t know if it would be better but you know that all their plans are based on ten years so they can say the other guy screwed it up.

Presidents do enough damage in eight years.  Personally, I'd like to see Presidents limited to ONE term of six years and members of Congress limited to a total of 12 years. 

No. FDR stayed in office too long, and became addled toward the end, and died in office due to a severe brain injury. FDR let Joseph Stalin have almost all of Eastern Europe. That would not have happened if he had some brains at the time. Then millions of people suffered for decades under Communist rule. 

And what we really need are term limits for Congress. 

"Not enough time" has never been an excuse used by capable people. 

No. The political system would work much better if we had term limits for Congress too.  

No.  The reason the Constitution was amended was because of Franklin Roosevelt.  He was elected to  four terms.  His replacement, Truman, decided two was enough.