Q&A #1 - Consistency and TSS, heart rate in intervals, and the utility of long slow distance rides and and race-pace training

Does consistency imply that Training Stress Score (TSS) should be relatively similar from week to week? How can/should TSS change over the course of the year/season? Should I run intervals to heart rate in hot conditions? Do I, or how often do I need to do long, slow, over-distance rides in half Ironman training? Do I need to do any run training at race intensity when preparing for a half Ironman?