[syslog-ng] Queueing of messages if remote loghost is down

I'd like to centralize logs from 2-data centers to my corporate offices via tcp destinations at my data centers and a tcp source at my corporate office. What if my data centers suffer network connectivity problems or I loose power at my corporate office? How long will syslog-ng keep queueing messages before I start loosing data? Will its attempts to retry connecting to my corporate office adversely affect overall system performance of the machine it is running on? Will it recover on its own after a few hours of lost connectivity? Thanks, Eric