My gardens are a hodge podge and news ones get shoved in wherever I find room.
There is an advantage to intermingling the divisions if you are interested in hybridizing seeing as neighboring lilies likely won't be compatible. Of course, this does not take the place of careful protection of pollen and stigma to ensure known parentage.
I do try to plant short ones in front but that is about it for planning.
Now if you are more into enjoyable landscaping that looks great and is color coordinated and all, that's great! But if I have a pink lily end up next to an orange one, well, c'est la vie!
