Is lithium is less reactive than sodium?
You can't just take the electrode potential as if that's going to correspond to the rate in which something is going to react.  For example, why do you think that aluminum is so stable in atmospheric conditions versus iron?  Aluminum forms a stable oxide layer that serves to protect it against further reaction, while iron oxide is weak, adheres poorly and is and porous.  There are numerous factors which affect a rate of reaction, and they vary in different situations.

Calculating rates of reaction is a very complicated thing, and it's usually easier / more accurate to just determine the Arrhenius parameters experimentally and use those.