I had it installed and it worked fine, I just didn't like the fact that I had to constantly update it (before I ran it) as there is little point in having this without it being fully up to date.
I'm not sure I understand your scenario here. The program itself needs updates only every few months or so. If you mean the vulnerability database updates, those are only done while PSI does its scan -- done either manually with
Scan > Start Scan or automatically every week or so -- and then only for the programs already installed on the computer. By "ran it", do you mean select "Start Scan" from the Scan pane? When PSI is launched, it's scanning for any changes to the installed programs, not updating the vulnerability info.
I don't have PSI configured to start up with my computer. I use it in Advanced mode, and unchecked
Settings > Start the Secunia PSI on boot. I launch PSI once a week while I'm connected to the Internet, let it take a few minutes to see if I've changed any of the programs (I don't think this is necessary, but it's just a background task anyhow.), and then select "Start Scan" from the Scan pane. On my small, slow computer the scan takes about nine minutes to scan its 20GB of files.
Perhaps you use PSI differently than I do, but I respect your decision that, for you, PSI is more trouble than it's worth.