Recently while commuting my road bike (drop bar) handlebars split in half at the stem while I was riding. I took a spill but was luckily mostly unhurt. However, this was the second time this had happened to me (the first was ~5 years ago, on a different bike) leaving me to wonder how I can avoid or anticipate something like this happening again in the future.

This bike had last been tuned up about a year ago, but I don't know if any level of maintenance would catch weakened handlebars like this. I live in an urban area in the US with enough bike infrastructure to get around relatively comfortably but not enough to avoid potholes, curbs and other bumps entirely.

Are there any visual or structural indicators that I can use to check for weakened handlebars in the future? Or is it just the case that if I'm biking regularly in an urban area I should plan on replacing my handlebars every couple years or so?

Edit: On suggestion I've attached an image of the handlebars after the accident. Unfortunately I couldn't find any of them intact.