Due to work travel, I'm typically only able to train Thurs-Sun. Therefore I am overloading in those 4 days. For example, on Thurs-Fri, I will do a high intensity workout twice during the day (1 hr our less) and on the weekends I will do long bike/long swim one day and long run/medium bike the other day. So I get Mon-Wed as rest/recovery. Is this a sustainable way to train? I typically do 4-5 events/year, including an Ironman late summer/early fall. Thanks for feedback.

I'd say that its sustainable
I'd say that its sustainable as long as you listen to your body. You're probably going to put a lot of pressure on yourself to go hard week in and week out because of your schedule, but you should still build in a recovery week every 3 or 4 weeks AND understand you may need to add in some unexpected easy weeks if you feel like you are getting burned out. Long story short, your body will probably tell you if it's sustainable... listen to it.
All other things being
All other things being equal, someone that trains every single day will outperform someone that trains the same amount of hours each week, but with 4 days of training, and 3 days off.
However, depending on your goals, the difference may be negnigable. Someone like myself that has done good to average 10+ hours of training per week and paced myself for a 12 hour IM, I doubt it would of mattered when in the week I trained. If you are in the 2 hour olympic distance range, and 9 hour IM range, that's when you notice the little things making a difference.
Just my opinion. I'm not a coach, trainer, doctor, and I don't plan on ever being any of them.