ATF Interval Extension Logic 722.6

[shertex]

So I understand that MB's current and settled recommendation is to replace the fluid and filter on the 722.6 transmission every 40k miles. However, it occurs to me that this is something of a one-size-fits-all recommendation that doesn't distinguish between trannies that HAVE a torque converter drain plug and those that DO NOT. The difference in the amount of fluid that gets replaced is significant.

So, assuming that MB's blanket recommendation errs on the safe side, would it not be reasonable to argue that, if you do have a TC drain plug, you could safely opt for a somewhat longer interval? My assumption here is that magnet cleaning and filter replacement at 40k is not absolutely critical....that fluid quality and cleanliness are the main issues. But perhaps that assumption is incorrect.

Also, if the main consideration is the fluid itself, why not do a topside extraction once prior to full service?

So, just thinking out loud, I was considering the following regimen on my E300s, both of which have TC drain plugs: fluid renewal via extraction and fill at, say, 50k miles and then full service at 70k miles. Is this a bad idea? If so, why? Perhaps I am underestimating the significance of timely filter replacement.