How can we increase sex time?

By making it longer.

How old are you?

How long of time do you go now? Are there health issues? What is your age?
A good healthy life style works wonders, if over weight lose weight, exercise get healthy and your sex life normally gets better also.

Next don't forget foreplay and/or after play women seldom climax from actual intercourse so you need to spend plenty of time before and after

You can move the clock ahead in the middle and say... look honey... it took longer than last time.

Hello San,

The duration of sexual intercourse largely falls on the mans ability to control his orgasm. As stated by others on of the best ways to have good healthy sex is by living a good healthy lifestyle. I posted the following paragraph on another thread but I think it may apply to you as well:

As Craven said there are condoms that can assist with prolonging the plateau phase where you are moving towards ejaculation. Any condom that boasts Benzocaine as an ingredient will have this effect. Condoms that have this ingredient include Durex pleasuremax. I personally do not like them (most men have faced this issue at one point in their lives), but you should try them for yourself. Also a snugger fitting condom will produce less friction on the glans, or head, of the penis. The glans are where most of the nerve ending are on the male genitals so lowering stimulation on this area can assist in delaying unwanted ejaculation. Furthermore a thicker condom will help.
Also practice makes perfect, find out how to control your body with your own body. There is no shame in masturbation and no one knows your body better than you so you are the only one who can truly find an answer for yourself (unless it's medically induced, then contact a doctor). I have found, from personally experience, that learning more about the process of orgasms has helped me to control my own. Goodluck with everything

I hope this helps in some way

-fdsaqwerish