A habit I started practicing years ago is to siphon/drain the trans fluid from the pan with every engine oil change. I get usually 35-50 % of the trans fluid changed doing this. At 30,000 mile intervals I pull the pan and replace the filter, wash out the pan sludge (not much there) and wipe off the magnet. This is the cheapest maintenance I can do for any of my cars. The trans fluid always looks and smells fresh, and never a tranny problem. I agree with you, 100K miles before a change, a "permanent fill"; no such thing !
I do this for the power steering as well. That fluid gets boiled and there isn't much to begin with. I've done this for my SLK

The AT dip stick tool; is yours like mine, about 2+ feet too long?
I had three guys check the part number, after I purchased it, and the Part Number on the bag is correct ! No wonder you can not consider it anything other than "a tool".