Old Man Judo

I'm new to judo but have been doing striking arts for some time. I've found that I have better conditioning than a number of the judoka in my dojo who've been at it a while and I attribute that to the interval training I do. You can do interval training a number of ways but I add four rounds of heavy bag work to the end of my weight training workout. Four rounds of 3 minutes each with one minute rest in between. Heartrate hits about 165 during the 3 minutes and gets back under 120 during the minute rest. I'm gassed at the end of our randori sessions but I've yet to take a break from one whereas many do. This is done 3 times a week in addition to judo (2x/wk) and kung fu (3x/wk).