They probably don't re-cement the landing areas every 2 weeks (in fact, i can pretty much guarantee they don't), but what they probably do do is to water-blast or chemical-blast away the rubber deposits that aircraft tires leave behind. The main problem is is that rubber makes the runway slippery (waterplane, etc), and it also eats away at the runway makrings.
I've heard from reliable sources that LAX does rubber removal on a different runway almost every night.
At MSY, we usually do rubber removal about once a year (which itself is probably not oftern enough), but then, we don't have LAX's or LHR's traffic.
Hope that helps.
Tom in NO (at MSY)
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina