Answer: The running type of liriope which you apparently have will eventually (probably sooner rather than later) fill in all by itself to make a very full, dense, carpeting of ground cover. It may also be difficult to contain in a given area, so you may want to think about how far you would like to allow it to go. A dug edge or "moat" of bare soil can work to contain it.
There are other types of liriope that stay in distinct clumps and expand only gradually, and these would need to be divided and planted on a regular spacing to achieve a similar coverage. In your case, this effort will not be needed.
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