I meant to discuss this a month ago but with a new addition to the family, finding the time has been a little more diffcult.
As we approach the end of Winter and begin to think of Spring us beekeepers must not be complacent. This time of the year is when we see many a demise of bee colonies due to starvation. My own observations have shown that bees tend to use little of their stores through until Christmas as the rearing of brood either slows or stops entirely for a period and rasing brood is the biggest drain on stores within a colony. A good heft at Christmas should give you an indication on whether you need to keep an eye on colonies over the next few months.
Normally (depending on the weather) brood rearing will begin to pick up during February and will increase exponentially as we move into March and April with the increase in temperatures and pollen availability, it is this sudden increase in laying that can quickly consume stores in a hive you thought felt 'ok' a few weeks before and this can often catch beekeepers out; only for them to return to a hive with bees head down in cells and dead. For this reason I advise you visit your hives more regularly during this period and check the weight. Some may ask "How do I know if there is enough stores in there?" My advice to you is to feel the weight of your hives at the end of the Winter when most of the stores have been consumed, this will give you an idea of what a colony low on stores feels like and therefore gives you a better idea throughout the Winter.
Another point to note is that all bees are different (unless you have an apiary full of F1s). I have colonies that have surprised me this winter with their frugal use of stores yet others have been on Fondant since late January and are consuming a patty a week... Don't just use one colony as a benchmark as to whether your other colonies need feeding, learn your bees and their needs on an individual basis. It is also worth noting that many of my colonies are now kept on national doubles throughout the year and appear to do very well with this scenario. It also suits me too as those colonies have more than enough stores and have required no feeding, these also appear to be my strongest colonies (far more so than the few I have on singles) at this stage of the year.
When it comes to feeding I have always been shocked with how much companies charge for 'bee food' which is basically fondant icing in a plastic packet (marketed for bees). I no longer pay their silly prices for fondant and instead buy in 12.5KG fondant icing from cake suppliers.
The fondant will keep fine as long as you keep it well wrapped in a plastic bag, any exposure to air will cause it to dry out. If it does dry out slightly, after cutting off a slice you can put this in the microwave for 20 seconds before rolling it out, After cutting it I place it on a piece of greaseproof paper and warm it in the microwave, I then place a piece of greasproof paper on top and roll it out thinly. Some people choose to use clingfilm but I have found that as the bees start to chew this up it can get dragged all through the hive and be difficult for them to remove whereas they seem to cut the paper into more manageable pieces to remove.
How thin you roll it is down to you, you dont have to roll it at all if you are happy to place it in a tub above the feeding hole but generally I prefer to feed fondant to bees that really need it and therefore i place the patty directly on top of the frames and hence it needs to be quite thin. One advantage to placing the patty in the hive (as well as more direct access) is that any condensation from the bees below actually helps to soften the fondant for the bees to take it.
Finally, feeding is also location specific. At this stage in March my bees in the countryside need to be building up in numbers ready for the Rape crop. You could therefore argue that now might be a better time to feed a liquid feed which encourages brood rearing rather than fondant. My city bees have a while to go yet before our Summer flow and as a result fondant seems to suit them fine.