Yes you can but I would leave undisturbed until they seem to be getting crowded and losing some of their flower-power. Mark where they are growing then wait until late summer/early autumn when the foliage has completely died and you are just left with dried stems. Then dig them up with a diging fork making sure that you do not damage the outer bulbs. You may find that you have a huge slab of bulbs so have something available to load it into. Allow them to dry off a little then brush off dry soil so that you can see what you are doing and carefully separate the individual bulbs. Lily bulbs are greedt feeders so I would refresh their growing position with fresh compost and replant the best bulbs as soon as possible rather than storing them. You should then have a lot of spares to give away!