I don't see how you can NOT do a pre-pre flight IF you only fly once a week or so.
Dunno about the rest of you, but I have covers on my wheels that pretty much prevent checking air pressure without removing them. So just to check the tire pressure is a 10 minute job (get the creeper, get on the creeper, pull up to the tire, unscrew three screws, check. And we haven't gotten the air compressor out yet, because we're just, you know, checking at this point.) I'm not saying this happens every time I go flying, but I check before a long trip if I haven't flown in a while.
It takes me 5 minutes just to clean the windows (ok, they're new and I'm cautious, but still... 5 windows, 1 minute per window, avg).
A pre-preflight allows time to correct the unexpected. It also should allow the actual preflight to go faster (assuming the plane is kept in a locked hangar, which I have).
In fact, pre-preflight is a lousy term. It's like pre-meeting meeting. How about "assurance check" or the "fix-it-now-before-your-pax-have-to-wait-while-you-fix-it" inspection.
and yes, aviatoreb... My preflights take foreever too. I try to treat each pre-flight like my airplane was sabotaged and I have to find the problem. I also happen to like looking at my plane.