With plain old Anki, 30-45 minutes of use a day should lead to B2/C1 fluency in a language like French or Spanish in 6 months. Level 2 languages (Greek, Hungarian, Hebrew) should take twice as much as French. Level 3 languages (Japanese, Chinese, Korean, Arabic) should take four times as much as French.
If 30-45 min/day is the sort of usage you’re expecting to give the app, I think you can plan out your subscription usage accordingly. If you’re planning on doing 60-90 minutes of app usage per day, then you need half as long of a subscription. (And if it’s more like 15-20 minutes a day, then twice as long.
If you’re already an intermediate, then knock off 30-50% of your subscription length.