If i decided to buy a link on monthly basis, then how frequently my PR changes according to the links i bought. I am asking this because, If my PR increase i can exchange link, may be 3 way link, with other web masters. so that i don't have to pay to the sites i have bought already on monthly basis. I may not clearly describe my question, Hope you guys understand and given me good suggestions.
Every time google updates, be it 3 months or 5 months from last update. However, your serps change within the week