There are a few things you can do. A lot of long-term couples forget about foreplay when they have sex. But, foreplay is important. In foreplay, focus on pleasing your wife and extending her pleasure. It will put less pressure when intercourse starts.

One of my best friends swears by this: have one beer before sex - it desensitizes him so that he lasts longer. It also makes him more relaxed emotionally. Works for him. I have not tried it.