Once you pruchased then it will be valid for lifetime for the end product but it will valid only for one end product (as like website). If you need to use the theme again for another website then you have to purchase individual license for each end producte (website).
If you purchased the theme from themeforest then theme license will be valif for lifetime.
All theme bundle plugins you will get free everytime you will download the theme update from your envato market account Download page.
Hi msgcoder - very good hints! Short question: what happen if you would like to remove the licence from one website and put it at another one? How the steps looks like in such case (if at all possible)?
Many thanks for your hints, advise,
Lasz
Simply you have to unregister the license and have to remove the theme from the old one then you will be able use the theme and theme license for the new one.
For any query or help you have to contact your purchased item author.