I current train for flat water kayak racing by doing 2 or 3 long days (2-4 hours) a week, 2 or 3 normal intervals (1-1.5 hours), and 1 or 2 rest days. But I've been able to do that because I work flexible hours. My flexible hour job is about to come to an end and I'm worried if I get a "9-5" type job, I won't have enough daylight to do longer workouts on work days. So I'm wondering if I can accomplish the same thing by doing my long days on the weekend, rest Mondays and Fridays and doing three consecutive HIIT days on Tues-Thu.
You can perform 3 consecutive HITT training sessions with no problem but you need to pay maximum attention to your diet and resting period for a good recovery for the next HITT session, otherwise you may not get as much benefit from the exercise as you expect. On the other hand, the longer the exercise the longer the recovery.(you need to rest at least 2-3 days to recover from long runs). Have fun
Of course you can. HIIT is very good for you and should be part of your normal workout regime.
Your program of fitness sounds pretty good.