Page "Illinois General Assembly" Paragraph 3

The Senate's term cycle is staggered.

In order to avoid complete turnovers in Senate membership ( except after an intervening Census ), not all districts elect senators simultaneously.

Every Senate district elects its members to serve two four-year terms and one two-year term per decade.

The placement of the two-year term in the decade varies from one district to another, with each district's terms defined as 2-4-4, 4-2-4, or 4-4-2.

Similar to the House, Senators are also elected without term limits.