Maybe not when he met Melian, but at the time of his death. It is possible he was on the third cycle of his life by then. Also, a "winter, as it were the hoar age of mortal Men" came upon him when Luthien died. Luthien cured him with a touch when she returned to life, but perhaps some trace of it lingered.
His pride got him in the end.
When I was a teenager, I pictured Thingol the way Elrond was drawn in the Rankin/Bass films.
Maybe not when he met Melian, but at the time of his death. It is possible he was on the third cycle of his life by then. Also, a "winter, as it were the hoar age of mortal Men" came upon him when Luthien died. Luthien cured him with a touch when she returned to life, but perhaps some trace of it lingered.