Times can congressmen be re-elected?
unfortunately, forever, or at least as long as they are alive. I assume you mean the U.S. Congress, not state houses.
Each of the 435 members of the House of Representatives serves a two-year term. The 100 Senators six-year terms. However, the majority of incumbent congressmen are often reelected to multiple terms. Since members of the House serve two-year terms, it can be said that Congress is reelected every 2 years.