I’ve been training with Xert for a few months now and am very satisfied. However, I’ve noticed that Xert keeps telling me I need to train more and more. Sure, if I want to improve, the load has to go up, but that can also be achieved—at least in part—through intensity. I set my availability to 7 hours, which is the absolute maximum for me. Initially, Xert told me I needed to train 6.5 hours to improve at the same rate; now it’s up to 8.5 hours, even though I’ve only selected “Moderate-1.” Should I switch to “Slow” and eventually to “Maintenance”? I find it hard to believe that, at my current fitness level (TP 175), it’s impossible to keep improving on just 7 hours a week.
Try changing IR to Slow and see if the Unachievable notice clears.
When Improvement Rate is >0 XATA will always tell you to ride more over time.
The higher the IR value the faster the rate of TL increase.
Eventually what goes up must come down. 
Changing improvement rate with XATA –
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When you reach max hours and want to level off, switch to Taper, purposely scale back to hours you’re comfortable with, then change to Maintenance.
At that point you can continue to improve by varying Focus Duration (FD) stimulus and ride blocks for X weeks at a time.
E.g. if you’ve been targeting GC Specialist (8-minute power), you might change to Puncheur (4-minute power) for 2-3 weeks. Then take a breather (rest week set to Off-Season) and change FD again.
During a Maintenance phase you can also deliberately pick the hardest workout amongst recommended workouts on HIT days. Or strive to higher Challenge Levels when using Magic Buckets. I.e. same FD target but you are condensing the time required to fill the buckets. That raises the Difficulty Score.
Thank you for the very detailed and valuable information.
I’ll try it this way.