This is a trick I use to keep the solution fresh longer.

The commerical dry powders sold for hummingbird feeders have Vit C in them to retard mold.

I buy one packet...usually about $1.00 at WalMart, and use about 1/4 measure to 3/4 measure of the sugar you would use for your particular volume. This will make it pink, and keep it fresher a bit longer. I also tend to make it a bit more concentrated, since this retards mold too. ( more like 1:4 instead of 1:5.) One packet lasts more than a season for me at this rate.

I have a small window feeder with a suction cup, so I mix small amounts at a time. If you use a large one like the picture shown, don't fill it up. Make only about 8-12oz at a time.
Large feeders will molder and rot before used up. Even upNorth where we have many hummers I only make a small amount of solution weekly. If the feeder is out of the sun, and on a Northern facing exposure it may last longer too.

I just love the hummers. I have some pics in my album that I have taken the past 3 yrs. Take a look!