I have been using Proviron for 2 years now at 50 mgs per day, and so far had no issues with it - only benefits. So you it is pretty safe to use it for a really long time, especially if you got some high quality proviron, such as Berd Pharmaceuticals. I don't think that 25 mgs is a good dosage, as the 50 mgs is the ideal dosage.