The pageURL variable (g) in Analytics has a limit of 255 characters/bytes.
The first 255 characters of the URL are passed along in g. If the URL goes beyond 255, it is captured in -g. This has a limit of 2k bytes.
If there are any processing rules/vista rules that need to take place based on the page URL, it works if the URL is not truncated. However, the reports will only show the g paramter, which is the initial 255 characters. The -g is only used for processing.