Temporal eligibility can reorganize a monitoring archive in directions that station loss alone does not predict. We characterized this instability in Caravan-Qual Lite version 1.1 over 2000–2020 using six constituents, country labels, 426 freshwater ecoregions, seven realms and Hill numbers q=0, 1 and 2. The primary rule retained 14,387 electrical-conductivity stations (Cohort A) and 4,373 stations jointly eligible for conductivity, phosphorus and dissolved oxygen (Cohort B). Across three-, five- and ten-year requirements, dissolved organic carbon lost 90.7% of stations while ecoregion q=2 increased from 3.909 to 6.594. Electrical conductivity and total phosphorus also gained q=2 ecoregion representation at selected thresholds, whereas dissolved oxygen declined across countries, ecoregions and realms. Nitrate and suspended solids realm q=2 rose slightly from three to five years before falling at ten. Thus comparable attrition did not imply a common geographic response. Equal-size references were treated as descriptive baselines rather than exchangeability tests. In Cohort B, ecoregion q=0 was 10.8% below its equal-size median while q=2 was 46.1% above it; a +0.5% within-country q=2 residual showed that the apparent evenness excess followed country composition, whereas the q=0 deficit persisted. Tightening seasonal coverage to all four quarters removed 40.1% of Cohort B stations and nine ecoregions and shifted country leverage. Temporal rules therefore changed country composition and FEOW representation in constituent- and order-specific ways that station retention alone could not summarize.