Direct comparison of multi-epoch PIONIER observations obtained using equal baselines for HD 37806, HD 50138, TW Hya, DX Cha, CPD-36 6759, HD 142527, and V856 Sco. Upper panels: absolute differences of the wavelength averaged squared visibilities (Eq. (6)) of all pairs obtained using equal baselines plotted against the time lag Δt. The baseline is indicated by the color. Lower panels: absolute differences of the wavelength averaged squared visibilities divided by the uncertainty σ (Eq. (7)). The gray shaded regions indicate where the differences are equal within the error bars (Δ⟨V² ⟩∕σ ≤ 1, see Sect. 4.1 for details).