"Ich gehe mit den Jahren."
This is not a valid German idiom. Google search for this phrase (in quotation marks) returns just 7 results - 5 of which are copies of the same text and one is the link to this discussion.
Is this a German idiom? It doesn't make sense to me, and I don't really think that learning nonsense sentences is going to improve my German.
My friend says it can be an answer to the question "How are you?" or "What's going on?" after not seeing someone for years. Then this answer means something like "Just getting older". It's not a sentence you will need often indeed and it's a pretty boring answer to give someone :p