Seems a little odd that as you ride more it becomes harder to get out. Cleaning out any dirt or rocks is the first step, I'll bet you have done that already. Now take a look at your shoes and cleats. Make sure the cleats have not worked loose and are free of excess debris. Take a sharp object and dislodge any dirt form the mounting bolts, make sure they are aligned properly and tighten them down. From there lube the pedal tension springs and give it a go. Don't wory so much about lubing the cleat/clip connection, it will dry out and get dirty very quickly. If everything else is in good shape you should be fine.