In an anime I heard this exchage:
A: 私は商業作家ですもの。仕事に対して全力で臨むのはいつの場合でも同じ
B: 次回作の小説遅れに遅れてるんです
Given that A is a novel author and is late in delivering her last work, I think B's phrase means something like "You say that despite being late in delivering your next work", but I'm not sure how I should understand the 遅れに遅れてる part, and I was unable to find info about it on my grammars or on grammar sites.
The only thing that comes to mind is taht it gives some sort of emphasis to the fact that A is late, but I didn't find any confirmation.