una solución rápida, pero depende (performance/precisión de validacion de la fecha, legibilidad) haría q cambie la solución
static string SplitAsStringFromDates(string text)
{
var matches = Regex.Matches(text, @"[0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2}", RegexOptions.Compiled);
var sb = new StringBuilder();
Match matched = null;
for (int i = 0; i < matches.Count; i++)
{
matched = matches[i];
if (i == matches.Count - 1)
sb.AppendLine(text.Substring(matched.Index));
else
sb.AppendLine(text.Substring(matched.Index, matches[i + 1].Index - matched.Index));
}
return sb.ToString();
}