Worms won't die in the soil; they are earthworms after all. However, if you want to keep them in your trench through the winter, you definitely do want to continue feeding them. If you live in a cold place, find yourself a horse manure or cow manure resource and add plenty of it to the top of the trench as the seasons get colder. The worms will love the manure and it will produce enough heat to keep them alive and around. You may also consider buying a composting thermometer so that you can check on them as the seasons change to make sure that they can still survive the weather. Then you will know if you need to add more manure for additional heat.

AMEN mamasworncomposting.
U can also cover the top of the trench with straw as you would plants for the winter. When U had waste , U could pull the straw back.
Good Luck.