I tend to agree with the premise that too many movements across the arc will be a factor in the longevity of the jack. In 2000 I purchased my dish from a little old lady who watched subscribed channels on the ten footer I now own. The lady told me she would move that dish back and forth many times a day to watch her favorite shows. Two years later the jack failed.

I purchased a used jack in 2002 (unknown brand) and replaced the old one. It is still operating perfectly probably due to less movement across the arc. The only time the dish is moved now, is when a mandatory blind scan is required.

I would guess location, temperatures and maintenance would also be a factor.