Sexlinks do tend to lay well. However, they're bred primarily so they can be color sexed at hatch.
Since their parents are normal chickens, their production shouldn't slow or stop at an early age.
This is from the feathersite.
"Bth Red and Black Sex-Links use a red male for the father. Either a Rhode Island Red or a New Hampshire may be used.
Black Sex-Links are produced using a Barred Rock as the mother. Both sexes hatch out black, but the males have a white dot on their heads. Pullets feather out black with some red in neck feathers. Males feather out with the Barred Rock pattern along with a few red feathers. Black Sex-Links are often referred to as Rock Reds.
Red Sex-Links are the result of various crosses. White Rocks with the silver factor (the dominant white gene would produce all white offspring) are crossed with a New Hampshire male to produce the Golden Comet. Silver Laced Wyandotte crossed with New Hampshire gives the Cinnamon Queen. Two other crosses are obtained with Rhode Island White x Rhode Island Red, and Delaware x Production Red."
http://www.feathersite.com/Poultry/CGP/Sex-links/BRKSexLink.html
These are not used for commercial production per se. The commercial egg farms use proprietary genetically selected birds but just because they lay like gangbusters their first 18 months and then become soup, that doesn't mean they can't lay for years to come.
Like all chickens, well managed, they can lay for many years but at a lower rate each year depending upon their genetics.