I don't see what all the stress is about. I make bottles fresh all the time (except the one overnight one, just out of habit more than anything) and it takes no time at all. I sterilise all the bottles twice a day (that's the only thing that's a pain in the ass), then when I need one, boil the kettle and make the bottle (takes about a minute) and then it cools in cold water while I change my daughter for about 5 minutes and then it's ready to eat. Generally, I know about how long she goes between feeds, so it's easy to anticipate when I need to put the kettle on. I used to use a flask, but just doing the kettle and making them fresh was so much easier (no flask to clean!). Formula smells and tastes better when it's fresh anyway. I find the nasty rotten cabbage smell only gets worse when they sit around. And there have been babies who've died from improperly made formula, so I figure since it's easy might as well do it the right way.
put a hot bottle in a bowl of cold water and you get leaks in through the holes in the bottom. It doesn't make a difference how tight you do it up or press the rubber seal in the bottom. I've always made in advance and lo has had no problems. If I were using a different type of bottles I would make day time ones fresh and probably keep nighttime ones in the fridge. If I'm out I take a sterile bottle and a bottle of ready made formula. Easy.
