This simple GreaseMonkey script for FireFox should work to keep you logged in at almost any sportsbook.
This is not a standard autorefresh script rather makes a HEAD request every X minutes for the last frame (or the entire page if no frames exist, or optionally a user-specified frame) on the page. By only submitting a HEAD request, the amount of data that's actually transmitted is extremely small (on the order of 300-400 bytes). The X minute timer is reset every time any page is requested from the site.
This script should effectively keep you logged-in to most HTTP-based site that times you out after a period of inactivity. It should do this without interfering in any way with your browsing. If a site relies too heavily on AJAX, however, the script might be ineffective.
To install, you'll need the the FireFox add-in GreaseMonkey. If you already have GreaseMonkey you can
install the Stay Logged-In Any Book script by clicking here. If you installed the previous the Bookmaker/CRIS-only version you should uninstall that.
If you don't already have GreaseMonkey visit the
FireFox GreaseMonkey page, install the add-in by clicking the "Install Now" button, then restart Firefox and install from the above link.
(If you want to uninstall, go to Tools/Manage User Scripts, select "Stay Logged-In", and click Uninstall.)
The script allows you to modify both the average and standard deviation of refresh times.