Checking in Luggage Musica, Venice, Italy

we are cruising on the Musica out of Venice, Italy on 22 April 2018, and our ship does not sail till 1700, I know, that you should check in 2 or 3 hours before. My question, how early can you check in your luggage? We would like to see more of the city, before we sail. Thank you.

Last time in Venice I could leave luggage around 11 without any problem.

thank you so much for responding, that helps.