It is recommended that players re-assess their hands at each turn. Rarely does a player keep their initial hand throughout the game; they typically pivot to a new hand as the game evolves and new information becomes available. 

So, as you receive new tiles, as tiles get discarded and as other players expose tiles, the computer will re-evaluate your odds of winning each hand and the recommendations may evolve over time.     

That being said, these are just suggestions. You're free to stick with a particular hand if you'd prefer.