It's absolutely pointless setting a set number of hours to revise per day because different people revise at different speeds. Some people would do perfectly fine with less than a week of revision, others would struggle immensely in three. I'd suggest working out exactly what you need to have revised and then spread the content over the days. By deciding what needs to be done rather than how long you're going to spend, you make it more likely that you're going to be able to revise enough.
Also remember that you don't need to have all revision done by the 6th May, you only need the revision for the exam you've got on that day done. You've got more time for the others.