I would like to ask you if there is any workaround,

when we add in a single line something today, if the next 3 months this field remains the same then do something (for example create a task).

I know that for a picklist there is something like picklist history, but what about other fields?
There is no need to be a single line, it could be a number field. And lets say that today we give the number 10 in the number field.
If this number (10) after 3 months is still in this field  then do something (trigger a workflow)