@Ken_Cook A few comments:
3,000 miles/week is a big step up from 1,000 (nice progress!), but not a lot of miles for someone who wants to achieve a significant endurance platform (although mileage isn’t a great measure) . I’ve been riding about 5k+ per year and that is just adequate. Serious endurance riders are 7/8k+.
100 miles per week is 5K/year. 3K is about 60mi.
100 miles/week at 4-5 hrs is 20-25mph. Even on flat roads, that is ridiculously FAST!!! That’s what Cat 1 and Pros do as their averages!
None of my comments above are meant to be critical. They are meant to suggest that it is important to have a accurate view of the investment you have made when analyzing your performance.
Perhaps, most important, is to understand the type of rider you are, known as your “Phenotype”. Generally speaking there are 4 types: Sprinter, Time Trialist, Climber and All-Arounder. Basically, what distinguishes them (i.e. where you fit) is the shape of your Power Distribution Curve (PDC), that is, how much power you can deliver over each time interval.
It doesn’t take a lot of analysis to see that you would fall into the Sprinter category (i.e. really high short term power, not so high 20min to multi-hour). Of course, through training you can improve any place along your PDC that you want (until you hit a genetic max). And as the saying goes: “Train your weaknesses; Race your strengths”.
Best of luck!