Since Line&Area chart v 1.0.9 reloading data automatically is possible. However I strongly recommend to turn off zoom function if you are going to use this function, otherwise the user may be confused if data reloads during zooming. The syntax is the same as in column chart:
<reload_data_interval>5</reload_data_interval>
would mean that data will be reloaded every 5 seconds.
As flash cashes data, there is one additional parameter:
<add_time_stamp>true</add_time_stamp>
this would mean that then loading data flash will add additional time stamp to url and data will be renewed every time.
For those, who tried to use this feature with column chart v 0.9.4 I suggest to upgrade to the newest version of column chart, as there was a bug: after some time of reloading data error occurred.