Balloons-Do they burst when filled with helium and released?

This is the question I pondered today as I and about a dozen friends watched balloons we’d released (biodegradable ones, I didn’t want to choke any sea turtles or dolphins) with notes attached for a dear friend that recently passed away. I overheard someone saying that when the balloons reach a certain altitude they burst and I was skeptical, skeptical enough to look it up. This is what I found. As the balloon rises, the air in the atmosphere gets thinner. At some point in altitude probably around 28,000 feet, the air pressure inside the balloon becomes greater than the air pressure outside the balloon. When that happens the balloon does go POP! Wind currents can play a part as well and may have since it was a rather blustery, nor’easter-y kind of day today. Cold air can cause the balloon to become stiff sooner than its maximum stretching point and hence burst earlier too. We watched our notes fly high and away against the steely gray of the cloudy skies today until they were specks too small to distinguish from the floaters in my old eyes and definitely too small to tell whether or not they burst. Regardless, I have faith that the thoughts we carefully penned and attached to our balloons found their destination, a place with Green Grass and High Tides forever.