I’ll have to find the details, or maybe ask about this on FQ. The pressure in the open space will increase in an opened and resealed bottle. That pressure comes from the release of more CO2. More than required to pressurize a warm air space. The cold soda can hold more CO2, but has to release it to the air space until the pressure equalizes. Each time you open the bottle you lose CO2, but more if it’s kept cold and resealed. I imagine an open bottle in the fridge loses less CO2 than an open bottle out of the fridge, but both go flat faster than is practical. If you don’t believe me get two bottles of soda try it out. Surprised me when I first heard this and had no explanation but testing proved it out.