Given that you've been doing it awhile without dying, the empirical evidence would suggest no. From a standpoint of overall cardiovascular risk the answer is probably also no. The conundrum is that there is a slight risk of sudden death during extreme efforts. However, the overall cardiovascular benefit of working out reduces your overall risk .
From a standpoint of getting faster, you do want to maximal efforts occassionally. However, they are hard on you, and need to be spaced with adequate recovery. You probably don't want to do maximal efforts such as power intervals more than once a week.