Whether the allegations you or a loved one face for OWI are days apart or decades apart, being accused of OWI more than once changes the process. This is because, if your OWI is tried, a second-time offender is viewed differently for lots of crime allegations, including OWI. Factors related the first OWI offense and the circumstances surrounding the second could have a big impact as well.
Mostly, in how serious the allegations are that one will face. If a person was convicted one or more OWIs previously if convicted again, the person will likely face stiffer penalties. Most notable is the potential for jail time, large fines, license revocation and other potential penalties if convicted. Under Wisconsin state law, if the OWIs were less than 10 years apart, included other's bodily harm and other factors, it can up the potential for consequences. Also, once a person passes their third OWI offense, the legal limit for that particular OWI offender changes from .08 to .02 for the sobriety threshold.
For those convicted or facing allegations for 1st time OWI, it's not as serious. This is mostly because Wisconsin views most first time OWI charges as a citation rather than a crime (unless bodily injury was involved) which will almost always up the level of severity of charges. However, this is an ideal experience to only have to go through once in a person's life. For those who unfortunately have to face OWI & traffic ticket allegations multiple times, it's clear that the process changes as the charges stack up.
Drunk driving is never advisable, and it is against the law. However, just because a person is accused of a crime doesn't make it true that the person committed that crime. Thus, a criminal defense is a realistic reaction to OWI accusations.