Scatter plots for various parameters for observations of loops undergoing decayless oscillations, as reported in past works (Wang et al. 2012; Nisticò et al. 2013; Anfinogentov et al. 2013, 2015; Anfinogentov & Nakariakov 2019; Zhong et al. 2022a,b; Gao et al. 2022, 2024; Li & Long 2023; Petrova et al. 2023; Shrivastav et al. 2024). Left: Relation between the period and the loop length, as well as the best linear fit for the long loops. Right: Relation between the kink speed and the loop length. The dashed lines at 50 Mm divide the short- and long-loop data. The blue circles correspond to the short loops, the black circles to the long loops (original data), and the red circles to the long loops, after adjusting the data for measuring the third harmonic.