In the last few days, I've noticed there haven't been any Intrusion Prevention updates at all. Do these only get updated infrequently?
You can always check the latest version released (and release history) here:
If you mean the IPS Definitions, then yes, they are only delivered when Symantec feels it's required. I checked my NIS 2011 LiveUpdate history and the last Norton 2011 IPS Definitions update I received was three days ago on 05-Nov-2011.
When you check the link Bombastus provided be sure to select your specific Norton product from the Select Product dropdown list.
Windows Vista Home Premium 32-bit SP2 * NIS 2011 v. 220.127.116.11 * IE 9.0 * Firefox 7.0.1HP Pavilion dv6835ca, Intel Core2Duo CPU T5550 @ 1.83 GHz, 3.0 GB RAM, NVIDIA GeForce 8400M GS
Thank you both for the helpful information and the info regarding the website.