I hesitate to call it a strategy, but with a long rides + variable temperatures you need to uncouple your fuel and fluids. What I mean is you want to keep your calorie intake roughly constant for each hour (up to max you can tolerate), but vary the amount of water you’re taking. If it’s really hot out, you might have to mix up your bottles at a weaker concentration of mix to make up for the fact you need to drink more bottles per hour. Or go from 2 bottles of mixed, to 1 bottle mix at your “normal” concentration and 1 bottle water (still have to drink more bottles per hour).
Conversely, in cold events where sweat losses are lower you might need an insanely concentrated mix to keep enough energy coming in without overhydrating having to stop and pee every 10 minutes.
Also keep in mind, sometimes the nausea is just your palette getting sick of the drink mix flavor, or even cravings for solid foods. When looking at several hours+, I think you need to look beyond purely carbs and get some protein. 30 hours? Something resembling a real meal or 2. The specific foods end up being very individual. One tactic is to have a large variety of snack foods available so you can pick and choose depending on what sounds good at the moment.