I put it in when my oil was 2000 miles old, so it wasnt very dark or dirty and still had a yellow tint to it. After adding seafoam in and ran the car for 100 miles, the oil was completely dark and thin, lossed its life or viscosity due to all the contaminants washed back into the oil. I didnt want to wait too close to the oil change because the oil would be too dirty by then in my opinion, because seafoam would add even more dirt to it so I was afraid driving with such dirty oil would harm my engine. Adding seafoam to the still good oil was my buffer to keep or protect the engine from running on oil thats too dirty.
According to many of the posters here, they do the 500, 1500k mile interval change etc. I guess they do that to completely flush out any remaining seafoam or dirt left in the motor. Seafoam didnt explicitly require that on their email to me, they just told me to change it out soon so your car wont run on dirty oil for too long or it can ruin the engine. After putting in fresh oil in my car, the oil was still fresh or yellow after 200 miles of driving so I didnt see the need to do the 500, 1500k interval just yet. I will keep monitoring the dipstick just in case and if it turns black when it hits 500 or 1500k, I will change it then. Why change it if its still clean in my opinion.