I typically mix up 2.5 gallons of Star San at a time. To sanitize my fermenting vessel(s), I pour about 2 quarts in and swirl it around to completely cover, then close it off until needed (I dump out the Star San solution right before I go to fill them). I submerge hoses, and small items until I need them. Anything too large to submerge in the solution I mix up gets sprayed. I (as with many here) keep a spray bottle of Star San available at all times. Never know when you'll need a quick squirt of it on something. Things like the liquid posts of kegs for example (before connecting up a line).
Remember, people, you ONLY need to sanitize things that come into contact with the wort POST BOIL... Mixing up 5 or 10 gallons per batch is making far too much. You can also continue to use the solution until the PH has gone up enough to make it ineffective as a sanitizer. Most say to do that when it hits a PH above 3.0. There's some saying the line is at 3.5.
BTW, Braufessor, you're going WAY over the top. If you're even moderately competent you can use the spray bottle method on a LOT of things. A heavy mist spray setting will cover items easily, quickly, and not use an excessive amount. I also use the bucket of Star San solution (2.5 gallons typically) to sanitize my flasks before pouring the starter wort into them (for the first starter step). IMO, submerging kegs is unwise at best. You're probably putting crud into the mix that you don't need to. 1-2 quarts poured in, the lid closed and pressurized to seal, and then swirled around is more than enough to do the job. I also run the Star San solution out the liquid tube to make sure that part is good. Of course, I also do that when cleaning my kegs (after they kick) so I don't worry about it later.