Remember: the key to copywork is depth and immersion, in addition to repetition. If you do too much, your kids will let you know by complaining, dragging their feet and doing inferior work.
Charlotte Mason talks about asking your child to give a full effort (with attention to excellent output) and then to stop. So even if all a child can muster in one sitting is a single beautiful letter of copywork, that can be enough while the child builds stamina, attention to detail, and commitment to excellence.
What that means is that if your child is giving you daily pages of handwriting or copywork and it is sloppy or not well executed, you are actually doing too much! You can ask your child:
Copy this passage and give me your best effort. When you feel your attention flag or you notice you aren’t wanting to continue, tell me.
Then you can stop and we’ll pick up tomorrow (or the next day).
What you are aiming for, then, is copywork that leads to growing ease and accuracy, not copywork and dictation every day that wears out the young writer.
I would round out the copywork/dictation practice with Poetry Teatime, read aloud, and conversations about words (word play, word games). I usually expected that my kids could do some form of copywork or a handwriting page most days when they were young (3-5 times a week). I only did French-style dictation or true dictation once a week and reverse dictation once a month.
Less is more. 🙂