i saw that 1:1 sugar syrup can mold on here, how long does it usually keep before it starts molding and it has to be thrown out?
All syrup will mold because of the pH and the concentration. How long it keeps depends GREATLY on the temperature, the cleanliness of the feeder, the heat that you took it too (the hotter, the longer it lasts) and if you shift the pH to slightly acidic. There is no way to give an estimate. I've seen syrup spoil in one day or two weeks assuming no pH adjustment and a clean feeder. With cool weather, an adjustment to the pH with ascorbic acid or some other organic acid, boiled water, a clean feeder, it will last longer than without those things. If you make it 2:1 it will last four or five times as long.
Mold can start at different times, depending on the atmosphere it is kept in. Mine mold all the time, but it doesn't slow the bees down. They still take it just fine.
You are talking about a critter that takes sugar out of old coke cans and water out of cow patties. A little mold won't slow them down at all.
Sure it will eventually mold, but... The bees should consume it before that happens. If they're not eating all it before it molds they may not require feeding at this time. Of course I'm talking about syrup given to the bees. If you are making batches of syrup, to be stored until fed to the bees, throw it in the refrigerator. It will last a month in there. OR, add 1 tablespoon of 'Apple Cider Vinegar' to each gallon of syrup. The bees have no problem with it and it acts as a natural preservative in the syrup; no more mold.
I have heard of putting a couple of tablespoons of Clorox in a gallon of 1:1 syrup will help stop the mold. Never tried it myself!