Sounds like your on a solid footing for future retirement. Good for you.
I spoke to a diesel instructor at our local Junior College who was a retired bus mechanic. He steered me to the 8.3. Claims he won't go near any bus with a wrench but he will talk about them. haha
I will be retiring in less than 2 years. I have the 444 and the 545 and will soon have all the time I need to go. Figure my daily distance will be 250 miles or less.
PS when I bicycle toured I was proud to do 80 miles in a day.