As long as you don't lose a weight, they will go the life of the tire in many cases. Sometimes not.
With the shape of the outside rim of so many wheels being different, they many times use the wrong weight type and they won't stay on.
It's getting easier to find a balancer who is familiar with using tape weights for the outside weight of the tire. The newer wheels are deep enough that they can put tape weights on the inside diameter of the wheel as outboard as possible. If you can find someone who will do this, they will stay in place. An added benefit is that they don't scratch up your wheels in the process. I've had very good luck with this method.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in