Seeing lots of friction material in the pan is not a healthy sign.
Ussually, you can judge the life of these by how many seconds it takes the reverse to engage. Longer means more wear.
I'd do another transmisson fluid change. The torque converter drain plug should be 5mm. Rotate the engine until it is down. You can disconnect the driverside hose going to the trans cooler .. and drain it as well( anothe 1/2 pint).
Other thing is the vacuum must be correct. Make sure your pump is working correctly, all the lines are connected. Commonly, worn-out switches on the valve cover or someone breaks the tee-fitting on the brakebooster line(big 1/2 diameter black plastic hard line).
If this doesn't help- start saving your pennys. Quality rebuilt transmission(ie all plates, bands, seals,etc..) give similar life to originals. Factory runs about $1800 wholesale and aftermarket boys are $1200-1500. IF you live in a big city, it's easier to find a MB transmission specalist.
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD