I just did this last weekend, and it did take about 15-20min with varying engine speeds. I was also surprised by the amount of Purge being returned to the jar by the return line. The "jar" method seemed to be a better way to make sure your injectors were really clean & removing & replacing the hoses was not really a big deal.
Best of all I was impressed how much smoother & responsive the motor in my 240 ran.

Aivars