My pediatric gastroentologist told me that my son can stay on Miralax for years. He explained that it will not have any side effects and will not cause a dependency issue. He said basically that it helps the stool absorb and keep water so that it stays soft.
The doctor suggested for us to try stopping it during the summer and see how the stools go. If we need to go back to it, then so be it. He suggested that we try again in December if summer didn't work out.
I hope this helps. If you need a referral, we see Dr. Jack An at Digestive Health Associates at Medical City. He is wonderful!