Will libido of men decrease after thirty.

Patient: Doctor,Does libido decrease after 30 yrs for men? If so, how to increase it. I do not smoke, I do not drink alcohol. Yet my friends warn me that libido decrease after 30 yrs and asking me to get married before 30. I am 28 years now and I feel to get into marriage after 30 because of career commitments. Kindly advise.Regards,Vivek