Yes, they're synonyms for something that has existed for a long time, and continues to exist. They can also be used differently: "Ageless" to describe someone or something that never seems to look old. "Timeless" to describe something unaffected by time or changes in fashion.

ageless means 'never growing old'. Peter Pan was ageless, he never grew up. timeless means 'unending, unaffected by time'. A great work of art can be timeless in that it is always relevant.