Hi Phil!
Stuart beat me to the draw while I was typing,
but I can add another data point in favor and several tips I've found ensure absolute success over years of use.
I have self-extracting crank bolts fitted to every one of my bikes with square-taper cranks, including the tandem. The ones I got are made by Sugino and were first on the market some years ago. They have continued to serve well n service for me ever since.
They were developed around a 6mm allen socket, and I wish it were 8mm. Still, I have never had a wobbly crank develop from their use. I employ a Shimano EX long-handled and hardened allen key from the late-1980s to install and remove them.
Most crank extractors need a few extra steps to ensure they will work properly down the road. These include...
1) Be sure to put anti-seize on the crank bolt threads and on the inside of the cap against which the crank bolt pushes to extract the cranks.
2) Make absolutely certain the thin copper washer included with most extractors goes between the cap and the bolt. Also make sure you have included the washer *under* the extractor bolt, in the socket of the crank arm. Both are necessary to make it all work, and you will rue the day you forgot them if you don't use both.
3) Make absolutely sure the cap is installed firmly in the crank with whatever tool is required. For my Suginos, this is a piece of folded steel with a hex-hole punched in the middle to take the key that drives it. For the others you linked to, it is a pin wrench.
4) For a first install, I would strongly recommend you lube the tapers in this application (yes, I know, a point of controversy) and then drive the cranks home using conventional bolts torqued to spec. Then, remove those conventional bolts and replace them with the allen-keyed versions, also torqued to spec. If you don't have an allen key bit for your torque wrench, you can get them acceptably tight by hand.
5) Check the bolts periodically, at ~60mi/100km intervals for several intervals. It is good insurance to make certain the cranks are driven fully home and seated squarely.
6) Thereafter, you should have no problem and no need to remove the cranks except on the road, when only a suitably long allen key will be needed. I have done this for the last 25 years or so and never had a problem, either on remote tours or closer to home.
7) One last note: If it has been awhile since you have extracted the cranks with these built-in extractors, do yourself a favor and dribble a single drop of oil into the gap between the cap and the extractor bolt. Removal will go ever so much easier.
To set your mind at ease, I would (and do!) use these things without hesitation and have not carried that "chunk of metal" (conventional extractor) since about 1997 with nary a worry or concern; you'll be fine, I'm sure.
Very best wishes on your final preparations and on the wonderful adventure to follow. You're in for a wonderful time, and you have all our best wishes for a safe, happy, and fun trip of a lifetime. Please keep us in the loop as you depart and -- hopefully! -- on occasion after you hit the road.
All the best,
Dan.
