I have been growing a collection of these for several years in 5 in pots. This year I have noticed that some of them are producing stems which are 3-4 inches long. At this stage the plant begins to lay over in the pot. What can I do to keep them at soil level?

Are you seeing the start of blooms?

There are no blooms.

Are you able to add a pic?

Sounds like bloom stems are developing. Yes, photos will help.

I think the stem of that one is rotting. It looks like the soil is pretty wet.

Maybe they are producing offshots ("chicks").

I see a mother rosette and an offset in the picture. Looks like the mother rosette was sitting pretty high on the stem stalk? I would check if the offset has developed any roots into the soil at point of contact. If so you can cut the offset from the mother rosette. I would be tempted to cut the big rosette from the main stem leaving an inch of stem from the rosette. Lay aside the rosette for its stem to callous and then replant into soil to develop new roots. Pull old stem and old roots out of the pot to make room for both mother rosette and its independent offset.

Thanks websemps, I believe you figured it out. It was raining when I took the photo but I am careful about the amount of water these guys get. I appreciate your thoughts.

Richard that is a great photo of your semp. In the other pots I see lots of moss. That is a sign that your soil mix is not draining fast enough. You might want to pot them all up with a faster draining mix.
Once potted be sure to add a nice thick layer of either chicken grit #2, or clean 1/4 minus sharp granite gravel.
What has happened, is the bottom leaves have been dying off, thus revealing the crown/stem of the rosette.
I agree with Bev, leave about 1/2" of the stem after removing all of the old dead leaves. Like Bev said, let the stem dry until calloused over. Be sure there is a nice layer of grit/gravel under the leaves when you replant.

What are you using for potting soil? I am seeing lots of dead leaves under the rosettes in the other pot.