This means that her husband beats her each time he gets drunk (repeated action) Напиваться (to get drunk) is a perfective verb. Perfective verbs don't have a present tense and use the future form to describe repeated or habitual actions.

In addition to Denis' answer - Russian has absolute and relative tenses (There are five absolute tenses in Russian - two past tenses, two future tenses and one present tense). The present tense can express any tenses (present, past and future). The past tenses can express past and future tenses. The future tenses can express future, present and past tenses. I think it is the higher level of the Russian grammar.