It is possible to get rid of decongestant dependency with the help of hormonal nasal spray. It's called Nasonex in Russia, don't know about international names. It takes a few weeks to kick in and suddenly you don't have to use any decongestant, then it takes a few weeks to slowly stop using hormonal spray.
I used it to get rid of horrible decongestant dependency. It worked like magic. Of couse, you have to be free of hormonophobia (some people prefer to die instead of taking hormonal drugs).