It is ideal to leave the large piece on for the whole time and just fix up the edges as needed. When it is applied it can actually slightly change the tattoo position and contour of your breast (depending on how good the person applying it is etc). Images are used to double check it hasn't been changed (and images are used regularly throughout treatment anyway) but by redoing it each week it allows for an extra degree of change but certainly nothing to worry about. Our patients have it on for 6 wks and as long as you don't face the shower and scrub the area you can wash as normal. Mines been on for 4 wks and no touch ups necessary.
Hope that helps x