Yes—aperture can significantly affect vignetting, so a flat-field made at f/2.8 may not accurately correct images shot at f/5.6, f/8, or f/11.3.

With many lenses, especially at wider apertures, edge shading changes because the entrance pupil is less visible from off-axis angles. Stopping down often reduces this vignetting. So a correction made wide open can overcorrect images taken at smaller apertures.

Focus distance can matter too, because focusing moves lens elements and may change the vignetting pattern.

So your original gain table is not strictly valid for different aperture settings, and possibly not for different focus distances either. Whether the error is acceptable depends on how precise your measurements need to be, but it is not safe to assume the change is negligible.

Best practice is to create separate flat-field calibrations for each aperture—and ideally each relevant focus setting—used in the real images. If you can’t re-shoot the integrating-sphere data, test the existing correction on representative images and check whether it introduces corner overcorrection or residual falloff.