This depends on how often you will be doing things like config archive, what your DFM polling interval is, how many syslog messages you will be sending, how often you will doing SWIM upgrades (and how big the images are), etc.  In general, with weekly config collections, a four minute DFM polling interval, 10 syslogs per minute, you are looking at very low bandwidth usage.  The syslogs take no more than 300 bytes per packet, and the SNMP+ICMP polling is about 2500 bytes every four minutes.  The config collection can be a spike depending on the size of the config, but those are generally no more than 32 KB.