If all seems ok to you, then keep driving on the old shocks.
However, find a speed hump in a neighborhood or parking lot. It you get more than one half cycle of bounce, that's a clue. But your mods may make this test irrelevant as you reference.
What happens to me is, the shocks fail slowly and almost imperceptively over time making subjective ratings hard. I usually don't realize how bad they've gotten until I replace them. But when I replaced the old OEM shocks at 25K miles with Koni FSD's, it was after my wife road in the back listening for a rattle and she said a bump almost raised her off the seat. She's got some spare time if you like to borrow her for a test ride.