We can tell you care about this plant because you’ve kept it for 20 years but the hard truth is that it will never be healthy or happy in the circumstances you describe. This is an Aglaonema and it is struggling. Your plant needs brighter light and it also needs a period of darkness. 24 hours of fluorescent light is not good. The fact that the soil stays wet is also cause for concern. This plant is fairly drought tolerant and should only be watered when the top half inch of soil is dry. If you water it once a week, even when the soil feels wet, then you are over watering and this can lead to root rot which can kill the plant. If it were our plant we would thank it for its service and add it to the compost pile. If you are determined to try to save it, you may attempt the following (but we make no promises it will work!)
1) Cut back all the stems EXCEPT THE ONE STEM WITH THE MOST LEAVES to about two inches above the soil. These leaves will photosynthesize to keep the plant alive while you try to stimulate new growth.
2) Bring the plant home and put it in an east or west facing window. If you can’t do this, forget about saving it. A grow light will not be sufficient to jump start a plant in such a sad condition.
3) Water ONLY when the top half inch of soil feels dry.
4) If and when you see new growth emerge from the cut stems and a few leaves have unfurled, cut back the one long stem to two inches above the soil.
If you decide to undertake this experiment, please let us know how it goes. Good luck!
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I just bought one of these at Walmart and the top soil is WET.