My experience has been similar. I've always struggled with pacing longer efforts. Now I can set up intervals with good targets based on testing, very effective from 5m to 20m. A lot of gains over the winter primarily on 20m Sweet Spot and 5m VO2 intervals. FTP is up 15% while loosing a few Kg. Another plus is my trainer work and outside work are equivalent. So when I put together a plan I can still stick to it if the weather is crap or I run out of daylight. That is a big reduction in the "cognitive training load".
The one thing I have not sorted out yet is a data based way to set targets for shorter intervals, say 1m range. I've been messing around with the WKO4 model which takes into account Pmax and FRC (Functional Reserve Capacity, or W' in GC) but so far have not really nailed it. Not as cut and dried at this point as purely aerobic efforts.