We have been on two very long cruises on HAL (both 30 days +)and have never noticed this effect at all.
We have noticed that the overall quality of food on cruise ships industry wide has declined somewhat, compared to, say ten or fifteen years ago.
Landlocked in Denver, but cruisin every chance we get.
Polynesia, Carib. '86
Cr. Odyssey, Scandinavia, '91, 30 Day S Pac. 2002
Crystal Harm, Aust., N.Z., '94
Royal Odyssey, AK,'96
Old Cr. Pr. Canal, '97
RCCL, Carib, 1998
Volendam, Car, 2000
Ryndam, 35 day S. Am., Antarctica, '03
Is. Pr., Canal, 2004
Statendam, 34 day China, Japan, AK '06
Cr.Pr., Carib. 08
Eurodam, Atlantic, Med. '10