Even in heavily lit tank, they eventually fall off at some point of time. You cant do anything about it. And replanting is quite a hectic job if you have to replant like 100s of stems in each type of species. Theres an exception for some plants like rotala wallichi, tonina belem, limnophilas for instance that dont produce side shoots, so their tops need to be replanted.
The trick is to hide the bottom halves of the stems by some means...as far as I have seen, good aquascapers do it by any of the following
1-by placing stems behind hardscape material and trim plants to that level.
2-low growing plants like blyxas, crypts, p. helferi, hydrocotyles, grasses are also used to visually block the lower ends of stems.
3-trimming a bunch of stems to form a steep sloping hedge also helps to a great extent
And also the bunch of plants with thick crowns cast a dark shadow and hide the lower ends. This along with a dark background effectively conceals the lower stems.