DAT sounds like what used to be a PVD (personal vacation day, borrowed against your existing allotment or next year's allotment).
Working double-double-single has always seemed like a safety issue the union willfully ignores. It implies you've had less than 8 hours of rest two days in a row.
I can do back to back doubles with no problem. Done it for years now. It depends on what I'm about to do in the future; ie: the following week. I usually do them near the weekend, or if I'm about to go on vacation and need some extra cash. Or I'm doing a favor for someone and doing their shift (along with mine). Most people are kind enough to return the favor if I need a day. Some people commute, so they can do back to backs with no problem, make up their hours, and then go home. Some guys are just out there trying to make money. I can't blame them! They are the ones making over 100K a year. It depends how motivated you are. When I was younger and single, I tried to make as much money as I could, (even with having a second job which I have for years) because you never know what the future lies in this crazy business - like being furloughed. Our system that we have now makes sure that you can't work over 16 hours. Some guys used to wind up working 18 hours (overlapping), or doing a double and then a couple of hours extra. Not anymore. The new system won't let you. And you can't even pick up a trade that will exceed your 16 hours (ie: picking up a overlapping shift in the same work area)