Expand 'age' comment

rust/src/events/serialize.rs

@@ -448,7 +448,9 @@ fn serialize_event_value(
     // We might not have an `age_ts`, e.g. if a remote server did not include
     // the `age` field in the event it sent us. Since `age_ts` is generated by
     // us, it *should* be an integer, but it is possible for it to be out of i64
-    // range. In that case, just omit `age` rather than erroring.
+    // range (e.g. if the original `age` was close to the maximum i64 value). In
+    // that case, just omit `age` rather than erroring (otherwise a once valid
+    // event could start failing).
     let unsigned = unsigned_mut(&mut d)?;
     if let Some(age_ts) = event.unsigned().age_ts()?.and_then(|n| n.as_i64()) {
         unsigned.insert(