I do not iron until a block is completely sewn and usually not until the entire quilt top is constructed. I have very few problems getting everything to meet where it needs to, BUT if I do need to make adjustments, it is so much more difficult to make the corrections if the seams have already been pressed. I am also not fond of spending the time it takes to press as I go nor do I like to keep my iron hot for hours at a time while I'm sewing.