Literal translation
Last as long as you will last, walk as long as you will walk.
Meaning
as long as it lasts, it lasts
Explanation
This repetitive formula plays on tautology to express the indefinite continuity of an action: duro que duraras repeats the same verb, dura, to last, once as an imperative and once in the future tense, as if to say the thing will simply continue for as long as it continues, with no fixed end in sight. The same device recurs in marcho que marcharas, with marcha, meaning to walk or to function. This echoing construction, typical of oral proverbial style, mimics through its very form the repetition and duration it describes: it goes on as long as the thing it names. It is used to comment on a situation, a process, or a habit that persists with no clear end or reason, often with mild fatalism or amused resignation before what escapes one's control. The double meaning of marcha, to walk and to function, lets the formula apply equally to a person on the move and to a machine, a business, or a routine that keeps going.