Hi Kate,
As I understand it, you're buying time slots so if you buy 30 days, you get 30 days from the time your subscription is activated. Personally I went straight ahead and bought Veena's lessons for a year and don't regret it at all!
I am self taught and pole three times a week at home, so effectively I'm only using the lessons for a fraction of the time I'm paying for. Having said this, they're the best I've seen despite buying numerous DVDs (another option if you think that would be better value for money for you, different ones are often discussed on the forums).
You can check out some of Veena's free lessons, they're linked in this post:
https://www.studioveena.com/forums/view/FREE_LESSONS__20110319122124
They're really clear but concise, you get demonstrations with a number of angles and Veena's great at listing points of contact too so you know exactly what you should be doing. I've also found Veena's very active on the forums and she will offer advice if you're struggling with something (as will everyone else here!).
Hope this helps! 🙂