Cenforce 25 mg, which contains sildenafil citrate (the active ingredient in Viagra), is used primarily to treat erectile dysfunction (ED). Generally, there is no significant risk of developing resistance to sildenafil with long-term use. However, there are a few factors to consider:

1. Tolerance: Some people may experience a decrease in effectiveness over time, which is more often due to changes in their underlying health rather than the drug itself. Conditions such as cardiovascular issues, diabetes, or hormone imbalances can affect the drug's efficacy.

2. Underlying health conditions: The effectiveness of Cenforce 25 mg may diminish if the underlying cause of ED worsens. If an individual's condition is progressive (e.g., diabetes, heart disease), it might appear as though the body is developing a "resistance" to the drug when in fact the issue is related to the progression of their health condition.

3. Proper use and dosage: For optimal effect, it's important to follow the prescribed dosage. Overuse or misuse of sildenafil (e.g., using it more frequently than recommended) may lead to side effects or diminished effectiveness.

If you notice a decrease in effectiveness over time, it is best to consult with a healthcare provider to rule out any underlying health issues or to explore other treatment options.