We have no canonical account of Mahtan's ultimate fate, but it's strongly implied that he remained behind in Aman when Fëanor led most of the Noldor back to Middle-earth. That's suggested by his evident regret at teaching his craft to Fëanor, and in The Shibboleth of Fëanor (in volume XII of The History of Middle-earth) it's explicitly said that he stayed in the West on the advice of the Vala Aulë. If he did indeed remain behind, then he presumably continued to live in Aman indefinitely.

Mahtan's name probably derives from the roots maƷ (literally 'hand', but implying skill) and tan ('craftsman, smith'). A possible alternative source for the first element of the name is mak ('sword'), in which case the name Mahtan would be interpreted 'swordsmith'.

It seems clear from late notes that Tolkien intended to change Mahtan's name, though he does not seem to have reached a definite choice for its replacement. Among the alternatives he considered were Aulendur ('devoted to Aulë') and Urundil ('lover of copper'; Mahtan was said to wear a copper band around his head). Though neither of these names found their way into the published Silmarillion, they do give us a small glimpse into the deeper background of the character.