This does not sound like "warmup" but rather like pre-stress. The purpose of warmup generally is to align your reflexes to the realities of today's state of voice and atmosphere and give an additional loosening up.
However, the durations you are talking about here would seem excessive for that. It rather sounds like your "warmup" is for getting your vocal folds a bit swollen so that you reach better closure. Similar effects would likely be attained by a few puffs on a cigarette (part of Caruso's warmup ritual, with his heavy smoking likely contributing to quite a few vocal health problems and to his untimely death), by partying and shouting a lot the night before (more effective than directly before since you still have a bit of the swelling but more relaxed folds), by chewing on a bit of habanero (beware of stomach cramps, though!).
All of that is not really all that sustainable. Somewhat more helpful may be staying well-hydrated (though you need to time this in order not to have to run to the toilet while performing).
But in the long run, you might need to ask yourself whether you are singing roles and ranges that you can deliver reliably and sustainably when you need to target a light inflammation of your vocal folds in order to achieve the closure you need for performing. Basically right now it seems that your voice needs to be in best condition for performing with a touch of crowbar on top. That's not something you can expect to deliver for decades.