Brief Answer:
It depends upon the causes

Detailed Answer:
Hi, thanks for your query. Welcome to HCM.

Erectile dysfunction can be due to psychological issues and medical problems.
At your age, it is mainly due to psychological issues like anxiety about the failures in the bed in past, anxiety about partner's satisfaction. Marital dysharmony, ongoing stress at home and at work place, excessive fatigue due to work etc. Any kind of stress predisposes to erectile dysfunction.

Stress distracts you during your sexual encounter and you lose your erection. It is sometime the faulty habit of penetration quickly without proper arousal and excitement.

I think you should go for sexual counselling and psychotherapy. There is a dual sex therapy for sexual dysfunction particularly erectile dysfunction. You can go for that by visiting a sexologist or psychiatrist. Tell him your problems and ask for help. You should also take your wife with you.

There is no need to take drugs like viagra, alprostadil injection, vacuum pump etc. at this age. In elderly when there is erectile dysfunction due to aging, diabetes, hypertension, neurological diseases etc. then only one should go for the drugs.

Work on you anxiety by regular exercise, relaxation exercise like yoga and meditation as well as breathing exercises.

During sex you have to give proper time for foreplay before going for penetration. Foreplay should continue even during the intercourse also. This is how you can hold your erection for longer.

Hope I have answered your query. If you have further query then feel free to ask.
Wish you good health and sex life.

---