I don't leave Jackson's on all day, but sometimes I will for a few hours at a time. He has a Puppia harness so it's mesh and comfortable and has never caused him any issues with matting, chafing, or irritation or anything. I think if you're going to leave one on all day to make sure it's a good and comfy harness.
Also, it's really easy to get his on. He knows the deal now and just puts his head down, Puppia slides over head, then he lifts his paw through the hole, and buckle, we're ready to go!