I brewed a keg of witbier for a wedding, and when I tasted it initially, as well as at the wedding, I did not notice a prominent DMS note. I am now drinking a glass and the DMS is nearly overwhelming. This is the very last bit of a keg that was kept warm for a day or so after the wedding.
Does exposure to oxygen increase the presence of DMS? The keg was dispensed with CO2, but there is always some O2 picked up on transfer, I suppose.