It appears to me that you get the greatest value from synthetics if they are used in conjunction with a bypass oil filtration system. This would allow extended oil drain intervals.
Driving as much as you do, I would think that you would benefit, a lot, from this combination. With as much driving as you do, you are probably changing oil every month to month & a half. This could get expensive & inconvenient. If I was in your situation, I would, seriously, look at doing this.
The conventional (regular) oils appear to be of high quality, nowadays. As long as you use a quality, diesel-rated oil. I've heard of people towing trailers for a living getting over a million miles on the Cummins engines & just using conventional oils. One in particular had 1,153,000 miles & used Shell Rotella 15X40, with 5000 mile oil change intervals & Fleetguard filters. This was back in the later '90's & the oils weren't as good as today, & we have better filters today, also (Stratopore).
Most of us will never wear-out our Cummins engines. Just won't keep them long enough. These engines seem to be easy on oil. But, if you are interested in the convenience of not having to go through the hassle of changing your oil every month, or so, then the synthetic oil & oil bypass filtration combination just may be the ticket, for you.
Joe F. (Buffalo)