Three to four one-hour Spanish lessons per week is a good baseline for most learners. It's hard to advance when practicing Spanish just one hour a week or less. On the other hand, having five or more per week can get tiring. Moreover, Spanish lessons shorter than 30 minutes don't allow enough time for much progress, while sessions longer than 120 minutes are hard to sit through without losing your interest, so 60 minutes is the sweet spot for most.