At one point - I was actually on the Rowasa for around 9 months or so - nightly. And I needed them. Every time I tried to slow down I would start getting symptomatic. 6-8 weeks is really not all that bad.
If you are still having problems retaining them - warming and squeezing out the air first are a must. Then my doc had me take 1/2 to 1 immodium 1/2 hour before taking the enema. Then starting with 1/2 bottle worked my way up to retaining the whole bottle over the course of a week. Eventually I didn't need the immodium anymore.