One of the issues we do face is that we have to do things in our lunch breaks anyway at the moment, any backed up paperwork or eyesight tests really have to be done then. What will end up happening across most test centres is tests on a Friday afternoon being cancelled go keep us within our contracted hours, if we have to work during lunch break or if not then after work.
The safety issue comes from exhaustion when completig an extra test, and the implications this could have individually on the test and accumulated throughout the week. A study was done about 10 years ago which reccomended to keep the limit at 7 tests, as it was shown that the safety of the 8th test was affected due to being overwhelmed and exhausted. The DVSA have decided that using ipads instead of paper now for our tests makes us less exhausted, I'm not sure why they think that as having a screen in front of yourself all day is a little harder on the eyes than a piece of paper.