I haven't been able to find out anything definitive about the dependency issue with Cascara, all of the people who have run into trouble have used Senna.

I've read several sources that say it is gentle and non-habit forming, and I've used it safely but for days off and on, not weeks steadily. Just to be careful I don't think you should use it steadily for more than 2-3 weeks, or if you do, follow it with triphala and/fiber, or just fiber w/o laxatives, and see how you do.

So really if you plan on using it long-term the only thing you can do is to occasionally go off it and see how you're doing. Make little reality checks. If you find yourself having to strain, or having incomplete voids, then there may be a weakening of the colon happening.

Sorry I can't be definitive, let us know how you do on it, that kind of real-world experience counts more than anything I can read! ;)