The web site says how fast it will go up with some quick maths I can tell you lol
How fast will the balloon ascend?
The balloon will ascend at about 1,000 feet per minute. At some points, its ascent could be as fast as 1,400 feet per minute. Upon reaching about 100,000 feet, however, it will likely slow to roughly 750 feet per minute until it levels off at approximately 120,000 feet above sea level.
Edit: around 2 hrs lol