You may break down too many proteins that are needed for body and head retention. The other concern would be having starch conversion nearly complete before you get to the alpha amylase range. If there are no starches left, the more complex sugars will not be created. Whether this has any impact or matters would depend on how quickly you can raise the temperature and what style you're going for. Might be a good way to make a high gravity beer or a very light beer. Not so good for a beer with big body.