Life expectancy of stem plants

[tiger15]

Do some stem plants have short life expectancy? I grow garden perennials and am aware that some perennials are short live requiring rejuvenation every few years by division or restarting from seeds. I’m asking the question as I’ve experienced decline in vigor in my narrow leaf Ludwigia, mermaid weed, and a few other stems which, after initial vigorous growth for a few years, then followed by gradual decline. I have been pruning out the bare bottoms and replanting the healthy tops but it only worked for a few years before the whole plant declined. This lost of vigor is not observed in my epiphytes, rosette and certain stem plants such as Rotala rotundifolia..