Write times with long exposures

Do you all notice long write to card times when using long exposure times.My GX20 seems to spend a proportionally longer time to write depending on exposure length.Is this common or a fault?

Many thanks mm

Dark Frame Subtraction is the culprit. With very long exposures the camera makes a second exposure in the dark and uses the noise pattern on that to subtract similar noise from the actual image.

This means that the exposures take at least twice as long whilst the camera goes through this process.

Many thanks for your speedy and comprehensive answer.

mm