Artificial valve lasts virtually a life time as long as you look after it carefully. One has to keep taking the blood thinning tablets and get the blood test (INR) done regularly to control the INR levels between 3.0 - 3.5) or as specified by your treating cardiologist.
2. Mechanical valve does not interfere in marital functions and you can safely get married and have a normal and blissful married life.
3. You can work and strain as much as you would like and there are no restrictions on this aspect.
4. Symptoms of a failing valve are usually sudden onset breathing difficulty, blood in sputum or sudden loss of consciousness of thinking sensation. If any breathing of this sort is ever noticed, then you must report to your nearest physician.
I hope I have answered all your queries to your satisfaction, but if you any doubts, please feel free to contact me and it shall be my pleasure to answer them.