In my household it's the only way for me to get training done.
If riding outdoors, up at 3:50am out the door by 4am and back by 6am, handover with my wife who might either go for a swim, run or jump on the trainer while I cook breakfast for the kids. When she's back I quickly jump in the shower, get ready and am out the door heading to work at ~7:40am.
Now I'll be the first to admit I can't do this year in year out consistently so every now and again I'll need a complete break from triathlons to focus on something else. I've been having a break since May (though never fully stopped and always done some stuff here and there) and am starting to get my shit together again for another campaign. It's hard work but fun at the same time to try and fit it all in.