This article explores whether differential time horizons in legislative chambers that result from staggered membership renewal affect legislative behaviour. The analysis focuses on patterns of bill initiation and the introduction of amendments in the upper chambers of Australia, France, Germany and Japan – all four of which contain two or more classes of members that face re-election at different times. Drawing on original comparative data, clear evidence is found of over-time variation in legislative activity levels in the upper chambers. Approaching elections lead to increased activity levels, with increases in the introduction of bills, but also, to a lesser extent, amending activity. Such variation is found not only for those members facing the most proximate election, but for all members of the chamber. Importantly, there are no significant differences in legislative behaviour between those members up for re-election and those not facing the electorate in the most proximate election. These patterns are interpreted tentatively as evidence of the paramount importance of political parties in parliamentary systems.