Unfortunately according to AR 27-10 the chain of command has 2 years from the date of the incident in which to implement an Article 15. FM 6.22 Appendix B which will be released in Feb (supposedly) as ATP 6.22-1 states the counseling will be conducted as close as possible to the event. It does not provide a specific timeframe.
Typically with a DUI off post the way it works is as follows. You get a DUI off post you are punished off post. They cannot give you an Article 15 for DUI. You can receive a General Officer Letter of Reprimand (this is administrative action not punitive). If there was any other misconduct your unit might be able to file an Article 15 for that. If you are not punished off post for the incident the Chain of Command could then initiate an Article 15 for the conduct…this not always true and is specific to the situation.