Sounds like it's losing its roots, like root rot. I suspect it's a drainage / mix problem. That doesn't seem like such a short time to me (4 yrs.), but that's not normal behavior for them (collapsing stem).

Pls. tell what's in your mix & how are you sure it's got good drainage?

Mine don't flower either, but that's not the issue, nor do I believe exposure is the problem.

Do you repot every so often? Have you repotted recently? And either way, what mix did you pot them in?

I bought this sans at my favourite (reputable) garden centre so I'm sure their mix is appropriate. The plant's in a plastic pot which is in another pot (clay) and I put wine corks in the bottom of the clay pot for additional drainage so the roots would not lie in water. As I mentioned, I water sporadically, so I don't think its too MUCH water (maybe not enough?). The stems seem to get weak, some flop over, and I removed 2 this past weekend that I was trying to "prop up".
The plant has not been transplanted since I bought it (adequate pot size for the size of the plant).

Is the garden center a greenhouse? If so, could be a different mix for that. We really need a pic pls.

Wait, is the mix 4 yrs. old? Or do I misunderstand?

If so, it could be the mix has hardened off completely impeding the plant from drinking, or there's little mix even left in the pot.

Wow, I just noticed there's Spellcheck on here now -- yipppeeee, thank you GW!!!

Keep giving good advise Karen. Wow spell check. That will save me a few steps.
Clairabelle,
Any sign of root mealies or any other problem like fungus? I have had Sans in the same pots for many years and never did anything to them. So I think it must be a tempature thing or something you are doing?

How do I post a pic? Directly from my computer? (excuse my French!)

Right above where you type below to post is a "browse" button for including a pic.

Duh! Should have opened my eyes... on the end of my nose :S

I'm thinking I should a) move the plant to a brighter location (it's presently near the kitchen door in low light) and b) water a bit more often (I was currently only watering once a month), and see how that goes.

I looked the soil over carefully and it was reallllly dry. I removed one of the drooping stems to examine the roots and the ball was intact and very dry, so... perhaps it's a case of "not enough water" rather than too much?

I'll follow this closely for a month of so and come back to report. Thanks to all of you for your support! YOU ROCK! :D