Time saved is most important when systems are down.
I documented all support contract info in standardized text files in a standardized directory structure. I had one central and kept more than one copy around.
Each bit of information (web portal, phone number, point of contact, expiry date, contract number, phone menu shortcuts, etc.) where preceded by a standard tag in old .ini format (tag:data).
Finding a phone number was as simple as going to the top level directory and running:
grep Phone */*support.txt | more
Where the first wildcard expanded to the vendor and/or product name.
I did not use Excel, Word, OpenOffice, a database, etc., etc., simply because when something is down, that something might be the very thing holding your support information. Also these are not easily viewable from a text mode console screen.
I also documented all how-to's in the same manner.