This is a tough question. Some ships that age may have a lot of wear and tear. Some ships that age may have been refurbished. Your best bet is to do your homework by talking to folks who have recently sailed on the ship you are thinking about or by reading the reveiws right here on Cruisemates. Just because a ship is 10 years old, doesn't necessarily mean you should avoid it.
Mary Lou Scanlon
NCL Pride of America April 24, 2010
NCL Epic February 12, 2011
RCCL Allure of the Seas - September 18, 2011
Celebrity Eclipse - February 11, 2012:
RCCL Navigator OTS - February 9, 2013
Our favorite Carnival ship is the Inspiration, and she would be considered "old" by some people. We sailed on the Miracle when she was only a year old and still liked the Inspiration better. I agree with MaryLou. If an older ship is getting good or great reviews I wouldn't hestiate to book a cruise on it.
Celebrity Century 1/09
Carnival Destiny 10/07
Carnival Destiny 9/06
Monarch of the Seas 3/06
Carnival Inspiration 8/05
Carnival Miracle 4/05
Carnival Inspiration 4/04
Sovereign of the Seas 4/03
Most ships are put into service with a life expectancy of 50 years. the ship may actually be sold or move to another line but if you research you will find there are many ships still sailing that are well over 30 or 40 years old. Carnival just recetly took the Jubilee out of their line up but all they did was renovate it and move it to their P&O line so they still have interest in the ship. I too really enjoy the Holiday which was Carnival's second purpose built ship. I have sailed her twice and would love to sail her again especially since she just came out of an extensive dry dock.