I have seams in my asphalt driveway. It's a big driveway and parking lot for my business, and I just couldn't afford to do it all at once. So I've done it in three section over the course of about seven years. I have had not problems with weeds or grass growing, nor any cracking or other issues. Yes, you can tell it was done in sections, but who cares? And when I get the whole thing re-sealed later, no one will be able to see it at all.