During winter, opening windows will raise your heating bills like mad.
Opening several windows/doors widely for a few minutes every couple of hours, rather than keeping one of them open for longer times, is supposed to mostly prevent this, as this will exchange the air in your room without significantly cooling down floor/walls/furniture. But of course you’re still right that it’s a trade-off, and for some people it’s much easier to achieve consistently good CO2 levels than for others. For many it may be worth at least getting a CO2 monitor to be able to make better informed decisions.
Opening several windows/doors widely for a few minutes every couple of hours, rather than keeping one of them open for longer times, is supposed to mostly prevent this, as this will exchange the air in your room without significantly cooling down floor/walls/furniture. But of course you’re still right that it’s a trade-off, and for some people it’s much easier to achieve consistently good CO2 levels than for others. For many it may be worth at least getting a CO2 monitor to be able to make better informed decisions.