I looked around on the Internet too and found many places that say "remember, NEVER remove plugs from an aluminum head when hot".
Well, I think the jury's still out on this one. I'm believing more and more that it's an old wive's tale.
Here's more real world evidence:
Drag racers (with aluminum heads) read their plugs between every round. Should we suggest to them that it's a bad idea because we read something on the Internet? How about every other kind of racer? They don't let their cars sit in the pits all night so the engine can cool. They dig in and start pulling plugs to see how things are looking.
I'm also an avid dirt biker (alum head). The most important part of setting up a new bike is jetting the carb. This involves running under load at fixed throttle settings and pulling the plug to read it. It's common to pull the plug 20 times within a few hours while tuning. This is done on every new bike, and it's done repeatedly to tune for different elevations.
I believe that the most common problem with plug threads in aluminum heads is due to cross threading and over-torqueing. Just my position on it, but I'm going to continue pulling plugs while warm.
Experience is something you don't get until just after you need it.