With regret i have to tell you that this will be something of a 'blue rinse' cruise i.e it will definately be an older crowd. Anyone that may have indicate dotherwise is very misinformed.
Are you cruising out of Australia? If you are maybe there will be younger partying people aboard, But generally people of your age group if they do a cruise of 25 days are travelling, with their parents - not alone due to costings, etc.
Anyone who can afford a 25 nt cruise will more than likely be retired...