Late in the season the tomatoes are way too tall so they get cut back. Has anyone ever let one or two suckers grow lower down on the plant earlier in the season so that they will take over and start producing when it's time to cut off the plants back? If so, when do you start letting a few grow for this purpose?

I know a better choice would be to just start some new plants for later production but that might not always be possible due to space issues.
I did start a Daniel Burson in early June and transplanted it into a bucket and it took the place of another tomato I had removed from the line. It's grown a whole lot and flowered a lot but no fruit ever grew until now... a new baby way up at the top and about the size of my finger nail so far. Maybe the shorter days have affected production. I've never grown this one before but started one after all the glowing recs here. It will be included in next spring's line up to get a fair trial. It sure is a big grower vegetatively!

suckers never produce
if you are concerned about height,keep topping the plant over the course of the season and clone the cuttings you take.

I’ve got I think 14 slicer or beefsteak type tomato plants still out there, not counting the 3 cherry tomatoes. All those out there went into the beds in February or March. There’s also a volunteer tomato plant.

A few of these I’ve cut away most of the foliage a couple of weeks ago. Those are putting on new growth. I’ve decided not to get any new tomato plants for fall. The next few weeks ought to reveal if there’s likely any production coming later in the fall from these old spring plants. As far as I can tell, only Beefmaster has set any fruit in the last couple of weeks. Others are blooming, but I’m not seeing fruit. Later in September into October I’m hoping for more fruit set. Maybe I’ll have tomatoes at Thanksgiving.

You want suckers from the middle of the plant to get production. Low suckers are no good. You can prune the main stems right back to where you want to start over. And avoid having to remove more suckers that are just too high up to manage without trouble.
When you prune back to start a new round of growth and production, it is worth the trouble to bleach your pruners between cuts. I put straight household bleach into a small container that I can dip into. Does not hurt the plant, the cuts remain clean and the stems don't get rot. That is your best insurance that the plant will stay healthy and keep on going.