Yesterday Wax was hanging laundry to dry on MIL's deck and the BB suddenly noticed the door and thought it was a balcony. She's never been outside outside except in a cat carrier, but she's got plenty of experience with balconies, which have always been safely fenced in places for her to hang out in the sunshine and watch the birds. So she immediately started yowling to go out there, and I got the idea that it might be good to give her what she wanted a bit, so I put her leash and harness on her and took her out there.
I know the BB has No Fear(TM) and that she would not actually hate being outside, but I thought she would take a while to acclimatize and not be quite as eager to go back out right away, going by her reaction to wearing the harness and leash before, or that she'd get so excited the adrenaline drop would tire her out when she came back inside.

No. She got over the leash pretty much... right away, and although she shows caution while moving outside, she doesn't really hesitate, she just carefully picks where she's going to go first. She spent most of her time eating grass and creeping back and forth, but I took her out twice yesterday, and far from scaring her off or tiring her out, she immediately entered Pining for the Fjords mode and spent about 3 hours total standing by the deck door yelling urgently to be let out.
Today Snookums saw us go out and awakened to the possibility, so he started flinging himself at the glass and yelling to come with before I even managed to get BB to the edge of the deck. So I came back in, wrangling the tiny perfection in an infuriated state ("But you SAID-") with one hand, put his harness on him, and took them both out. Snookums, because he's a giant fraidy cat, was much slower and more cautious and it was challenging to hold on to both because he wanted to take it much slower whereas she was ready to go exploring.

Eventually he came down from the deck to investigate the grass she was eating, but then a neighbor came outside and walked by and that completely did him in; he sank down onto his belly in the grass next to the BB and didn't move a muscle until they were gone, and then he went right back up to the deck and asked to go back inside.

So I dragged the BB back there to let him inside and take his harness off and closed the door behind him, and only then did he realize that BB and I were going to stay out there without him and so he spent the whole rest of the time anxiously peering from the window and occasionally saying "Mwow?"

When I finally took the BB back inside, he sniffed her carefully, presumably checking to make sure she was okay.
I know the BB has No Fear(TM) and that she would not actually hate being outside, but I thought she would take a while to acclimatize and not be quite as eager to go back out right away, going by her reaction to wearing the harness and leash before, or that she'd get so excited the adrenaline drop would tire her out when she came back inside.

No. She got over the leash pretty much... right away, and although she shows caution while moving outside, she doesn't really hesitate, she just carefully picks where she's going to go first. She spent most of her time eating grass and creeping back and forth, but I took her out twice yesterday, and far from scaring her off or tiring her out, she immediately entered Pining for the Fjords mode and spent about 3 hours total standing by the deck door yelling urgently to be let out.
Today Snookums saw us go out and awakened to the possibility, so he started flinging himself at the glass and yelling to come with before I even managed to get BB to the edge of the deck. So I came back in, wrangling the tiny perfection in an infuriated state ("But you SAID-") with one hand, put his harness on him, and took them both out. Snookums, because he's a giant fraidy cat, was much slower and more cautious and it was challenging to hold on to both because he wanted to take it much slower whereas she was ready to go exploring.

Eventually he came down from the deck to investigate the grass she was eating, but then a neighbor came outside and walked by and that completely did him in; he sank down onto his belly in the grass next to the BB and didn't move a muscle until they were gone, and then he went right back up to the deck and asked to go back inside.

So I dragged the BB back there to let him inside and take his harness off and closed the door behind him, and only then did he realize that BB and I were going to stay out there without him and so he spent the whole rest of the time anxiously peering from the window and occasionally saying "Mwow?"

When I finally took the BB back inside, he sniffed her carefully, presumably checking to make sure she was okay.