Actually, I would think that...
...in order to REALLY get everything out of the oil pan cracking open the drain plug every once and a while would tend to get any of the heavier stuff congregating on the bottom out of the engine.
The Topsider system sure seems to be convenient but I just don't see how a tube is going to get all the gunk that settles down by weight on the bottom.
At least during an Auto-Rx application I would get down there and see what comes out, perhaps even after using the Topsider: if you opened the drain plug and 6 more oz. of goo drained out it wouldn't be in there anymore, would it?
Interesting to find out...
'91 420 SEL @ 199K, '92 SVX @ 181K, '93 SC400 @ 86K, '93 Kaw ZX-11 @ 30K, '87 F250 @ 181K , 2001 Valkyrie Interstate @ 6K, Y2K Honda NightHawk 250 with 1.5K, '88 420SEL I.@ 179K & the 2nd latest, an '88 420SEL II.@ 210K runnin' parts car, '85 F150 300/NP435