I would think about three to six months.

If your rats are depressed, they may prefer ice cream. However, I would recommend NOT getting such large bags! Two pound bags are probably best, because if it gets stale, the rats will stop eating it. Two pounds will last much longer than you might think. You will have to determine the correct amount to feed them. If you find them storing it, cut back on the amount -- otherwise it will be wasted when it becomes urine soaked. I have had rats for over 20 years and I feed them "cafeteria style," which every Vet that I have talked to, agrees with. Lab blocks are the primary meal, but they will love (and benefit) from little pieces of your own dinner. Nuts and fresh raw vegetables are also good (except green peppers which all of my rats have refused to eat). Despite what some "experts" say, even a tiny piece of chocolate is OK. Just not too many calories. Rats teeth are continually growing, which can become a problem as they get older (DO NOT EVER let a Vet trim their teeth). Get hard dog biscuits to offer as an alternative to the blocks once or twice a week. They like the change and it helps to keep their teeth worn down, naturallly. If your rats start chewing things that they should not, get the smallest rawhide sticks (made in USA) that you can find, as a substitute.

The healthiest food is the one given in moderation. I have NEVER seen an underweight rat, so you don't have to worry about that! However, it is easy to overfeed them. As with me, if the food is in front of me, I'll keep nibbling at it. With "loose" food, I am guessing that it is easy to overfeed, plus the cage gets messed up sooner. Food gets hidden and soiled, and then it spoils. It is best to feed lab blocks as the main diet. One a day is more than enough. So, once or twice a week, I feed them less but add a tiny piece of raw fruit or vegetable; too much and it will get messy. Each rat is an individual and will pick and choose it's own favorite foods. A piece of hard dog biscuit as a once a week alternative will help to keep the teeth worn down and you'll find the rat snatching these out of your hand. The only thing that interupts a rat sleeping, is when you start eating yourself!!! Keep the cage in an active area of the house and they will adapt to your schedule. If you have a pair (that get along) they will play whenever they want, but when they are awake, they will appreciate all of the attention that you have to give. Long life!!!! That is a tough one. My best advi ce is to quit reading books about what you HAVE to do. My rats are living longer than ever, because I have stopped trying to do what is "right." There are some common sense things like keeping them out of drafts (all year long) and giving them a variety of foods, but there is no guarantee. If you are really concerned, give them bottled instead of tap water. Keep in mind that chemicals in our water provide a much more concentrated dose to our rodents because of the difference in body weights. Also, honestly, do you drink tap water all day? Or do you drink milk, orange juice, soda, coffee or beer (yes, my rats receive an occasional taste). Everything needs to be in moderation, and when you are filling the water bottle, is you can smell chemicals from the water, give a second thought to using cheap bottled water.