I used to give a half hour for writing groups, but most times I'll allow 45 minutes because I think the time spent is valuable. I want them to focus on looking at each other's paper. I think they learn a lot that way. It's also much more interesting because they're sharing ideas. The evaluation criteria sheet helps me and helps students see where they are having problems.
Accents can be a terrible problem.
Hopefully it will ring a bell and make them work harder.