How much is your repeat for the lace? I would place stitch markers after every repeat or every few repeats so that you can check on yourself to come out right. that will be a great help with your project in general. The life lines are a really good idea, too. Do yourself a favor and don't rip each one straight out, when you have come to the next. keep one or two as a backdrop. then you can decide how far you go back when needed.
in some lace you can only start to see mistakes once you have gone a good bit further.
Good luck to you and let the needles click away!