As a compromise between completely open or close objectives, you could also say that any Objective Cards in excess of two Objective cards (say) must be revealed which stops people from stockpiling them in secret but also keeps a certain level of secrecy in the game.
This could also act as a bit of a leveller as people who are amassing more objectives are probably likely to be in better position. If you have more than 2 objectives amassed then other players are now able to strategically play to try to prevent you from attaining those extra objectives (which in turn affects how you strategically play in trying to fulfil your objectives).
This gives some more strategic options/decisions for play (which objective to keep hidden or revealed).
Robert.
This could also act as a bit of a leveller as people who are amassing more objectives are probably likely to be in better position. If you have more than 2 objectives amassed then other players are now able to strategically play to try to prevent you from attaining those extra objectives (which in turn affects how you strategically play in trying to fulfil your objectives).
This gives some more strategic options/decisions for play (which objective to keep hidden or revealed).
Robert.