When shall I cast off?

[Flossyfloof]

I am knitting a very simple baby blanket with a sewn-on border. The pattern repeat is 12 rows but all knit and purl rows with the exception of rows 5 and 11. So you knit 4 rows beofe a pattern row. Finishing instructions say to finish on a row 4 or a row 10 and to cast off in pattern. I have knitted this blanket several times before but ages ago and I can't remember what I did. It doesn't sound right, though, does it, to cast off on a pattern row? To make it more consistent with the bottom I a, thinking of casting off purl wise on row 3.
Hope that makes sense! What do you think?

Difficult to say without knowing what the pattern is! For example, if it's a pattern that involves slipping stitches, that would look a mess I think on a cast off row.

I think I'd decide on the basis of how you want it to look.

Thanks both. Oh bugger I was thinking that rows 4/10 were pattern town so I would be yon and k2tog ing in the midst of casting off. Of course that is not the case! Thanks both, yes I will cast off purl wise on row 4. No idea whT I was thinking, I couldn't understand how I had knitted this do many times before and not altered the pattern to make it more sensible! Now I see it us me who requires alteration! Thanks both.