I work on both types of screw and can recommend models from both Camps.
In simple terms "You get what you pay for". Yes Hall Screws are High Maintenace. Compaired with some cheaper " sealed for life" twin screws.
But when you refer to a Halls maintenace manual.
It says something like " Every 24 years or 100,000 hrs (11.4 yrs of running) Renew the main bearings.
That's pretty impressive in my book.
More importantly when they do go wrong you can repair them. Because the Star wheel is sacraficial compared to comprable damage on a twin screw.
Likewise I have a site with 2 stahl (twin) screws ( On Ammonia) that in nearly 20 yrs have only needed Oil Filter changes and a shaft seal each.
Brilliant Machines no longer made ( to well engineered making them expensive to produce. I Believe?)
To often equipment is purchased purely on cost and not longevity nowadays.
There appears to be cheap twin screw models out there that are supplied on a disposable basis. When it breaks rip it out and put another one in. These cannot be compaired with the more expensive and reliable models from both camps.
Yes I did work for J&E Hall.
But I can appreciate good kit wherever it is made.
Sometimes good equipment fails because those looking after it are not up to the job!
Grizzly