Saddle bag or jersey pockets?

Tools and such in the bag, tubular tire strapped underneath that with an old school toe clip strap.

The only thing that goes on my person will be some gel packets or a gel bottle.

I've had plenty of flats.  I never take the saddlebag off.  Like others have said, just keep you tool and tire supplies (and maybe a spare $20) in the bag, and leave it alone.  Snacks, cell phone, basically anything that doesn't "live" on the bike, goes elsewhere (jersey pocket, bento box, camelback, whatever).

The only other thing to remember is to replace anything that got used (it's REALLY inconvenient to get you next flat and realize the "spare" is the last flat...

Why would you be stuffing things in during transition? Saddle bag and or bento box, anything like a gel or something that would go in my tri tank are usually taped to my bike,

You also wait an indeterminate time for a ride back, or walk as much as 12 miles back to the transition area. With a spare, at least you have a ride home.

I was thinking the same thing.  I've got a 19.5m (one loop) bike portion in my next sprint, and I wouldn't want to walk back 1 mile, much less almost 10 in bare feet.  Walking in cleats would be even worse.

x3.  There's no good reason to not just leave the emergency supplies on the bike. It's highly unlikely that your time will be affected by their weight and it's one less thing to fiddle with. I mean, do you take the spare out of your car because you are not driving very far? After all, gas mileage is affected by the total weight of the vehicle, and with gas north of $3.50/gallon who knows how much money you would save...