A worthwhile modification employed by some schools is that of practicing the basics in reverse. Upper blocks, reverse punches, front kicks — indeed, any basic technique normally done while advancing — can also be practiced while stepping backward.
Although a bit awkward, blocks are more likely to be used in conjunction with some type of retreat or evasive measure rather than when stepping toward an attacker. This is not a hard and fast rule; however, it is the way it often happens for real.
Likewise, kicks and punches must frequently be delivered while backpedaling from a charging foe. By training exclusively while advancing, you may have difficulty summoning stopping power if you suddenly have to launch a technique while backing up.