Men in their 20s are more active and possess fast metabolic rates as they can be good in bed even after having a tiresome day. How can this not be possible in your 30s? This is because you have hit your 30s and there is a lot of difference in the peak you had in your previous ages. To understand this change is quite critical, as what you do during these changes affects your overall sexual health. 
The male menopause also known as andropause starts hitting individuals as early as 35. During this stage, there is a drop in the libido and even can cause erectile dysfunctions. 
How do you avoid this? Here what you can do on a regular basis to keep yourself fit at all times so you can be fit when it matters the most! 
-Check your family medical history 
-Check your testosterone levels proactively 
-Eliminate artificial sweeteners 
-Keep a check on your alcohol consumption 
-Dump the junk and add more veggies to the palate 
-Get a lot of sleep 
1. Check your family medical history - Family history is an important determinant to understand the faults in one's genetic DNA. It matters even though you and your family must be living a different lifestyle or live in a different environment, but as they say, it is all in the genes. You can still lead a healthy sex life if you are active and fit at times available to you. 
2. Check your testosterone levels proactively - Declining levels of testosterone brings a lot of problems such as hair loss, decreased sex drive, depression and memory levels which is again a vicious cycle. To avoid this, include meat, fish, cheese and yogurt in your regular diet. 
3. Eliminate artificial sweeteners - Sugar may not be our strongest friend but it is our strongest foe for it all does other than lessening sweetness in our morning tea/coffee/diet soda but also increases the risk of developing non-Hodgkin's lymphoma. 
4. Keep a check on your alcohol consumption - It is okay if we gulp down a drink or two of red winedaily, but if it is more than that, then you can say good bye to love making sessions as excessive drinking can not only destroy your liver and your gut and so on but also impair your libido. The key here is just moderation. 
5. Get a lot of sleep - A minimum 6 hours of sleep is ideal as it helps your brain health, manages your stress levels and most importantly optimizes the male hormone production which helps you in a healthy libido to satiate your partner. Men who sleep lesser than 6 hours have an increased risk of stroke and heart disease as well. So take care of your body while you can before it's too late!
In case you have a concern or query you can always consult an expert & get answers to your questions!.