Up down pays

Hero members will receive: 0.0014BTC  = 0.62 USD
Senior:    0.0012BTC  = 0.53 USD
Full:        0.0008BTC  = 0.35 USD
Members: 0.0006BTC =   0.26 USD   

With a 200 post limit at senior level that's $100 usd per week, is signature campaigns really worth it. How long does it take to get to each of these member statuses? To reach jnr member is it based on how long you are active or is it a set time?