If someone had never actually practiced aikido in the dojo, would you consider them ever able to "do" aikido in the rest of their life?
Since that would be the whole point of training, I would answer that question, "no." However, I would answer that question the same for anyone that is training but that is not training daily, that is training but that is not training in intense live-training environments, that is training but that is not working to develop a connection or relationship with the Sacred/Divine, or that is training but that has not problematized their ethical self. Like the person that has never actually trained, this other type of person that is training but not as described above is only likely to practice the art under the more pristine conditions of life - not all conditions of life, and thus not in the "rest of their life." This will be true whether we are talking about defending yourself in a real life and death violent struggle for survival or whether we are talking about having a crappy boss or whether one's marriage is on the rocks, etc.