Once they're out, you're committed to stop because you don't know if, and how quickly/symmetrically, they'll stow. Even with a long, long runway, if you push up the power and one reverser is still out, you're going off the side -- one side of the aircraft is producing forward thrust, the other is producing reverse thrust, you're done!
All the safety interlocks & features in the TR's are all about preventing uncommanded deployment -- since that might well be unsurvivable in flight. But when you HAVE commanded the deployment, those safety features are all satisfied. There isn't any similar level of engineering to guarantee that they stow, and do so simultaneously, because you're simply TOLD, don't try to take off once the TR's are out.
If one fails to stow at the end of the landing roll, the effect is pretty minimal with the power at idle and the aircraft at or near taxi speed, so in general there aren't great issues with the TR's perhaps still out after you're done with them. The one case where it's a grave issue is handled with a policy solution ("don't") rather than an engineering solution.
As far as realizing that you touched down too long and you need to take it back airborne rather than trying to stop, that IS possible... right up until the point that you deploy the TR's. Then you're committed.