I responded in the other thread. I would say no need to change filter midstream.
Right now I'm approaching 10K miles, 13 months on my 850 OCI (110,000 miles total). I'm using Amsoil SAE (10W)-30 ACD HD Diesel in that one, and have used Amsoil 5w30 ASL in the past (20K OCI) - but usually do 10K intervals, depending on how many miles I get in one year. I've gone over a year this time, because I messed up my neck and don't feel comfortable changing oil right now. I'm not particularly worried. Soon I will change it, though.
Anyhow - I'm not sure what oil I will use this time. I always use a different Amsoil. I may even try the HDD 5w30 or AME 15w40.
On the topic of the XW-40 I would never use a 15w40 conventional, especially in winter. It's interesting that my manual calls out 15w40 as acceptable. Over the years, the XW-40's have just run quieter, but in reality I can't say the UOA's are any different.
In Georgia, midsummer I lean toward an XW-40. But if you feel more comfortable following the manual, then a good 10w30 will be perfectly fine.