Does my proposal have a higher chance of being approved if I propose a short programme?

No. The only key criteria for approval are the scientific excellence and feasibility of your idea, as well as its alignment with the ESO’s observing policies. The review panels are instructed to evaluate proposals solely on their scientific merit and the strength of their justification.

When writing your proposal, you should focus on defining the best strategy to optimise the use of telescope time, but not at the expense of your science. Don’t reduce your requested time if it means compromising your goals. Ask for the time you genuinely need to achieve your objectives: if that’s 3 hours, ask for 3; if it’s 70, ask for 70.