2-3 days if there is no cream filling.
To keep your cupcakes as delicious as when they were just baked, take a few steps to prevent them from drying out or spoiling. Depending on your storage methods, cupcakes can be stored for as long as six months. Room Temperature. Most homemade cupcakes will be safe at room temperature for one to two days. To ensure freshness, store the cupcakes in a covered airtight container. If you do not have an airtight container, cover the cupcakes with several layers of plastic wrap. Cupcake Tip #1: Keeping Cupcakes Fresh If you want to keep your cupcakes fresh and soft DO NOT put them in the refrigerator, it will dry them out. You may put the unfrosted cupcakes in a container and wrap container in saran wrap to freeze them. I find that cupcakes keep best when stored in an airtight container and left on the counter in a cool kitchen – good for 2-3 days if there is no cream filling/frosting. I use mostly buttercreams and the high sugar content keeps the butter from going bad. 1 Unfrosted cupcakes that do not contain filling made with dairy products or eggs (such as buttercream, whipped cream or custard fillings) may be kept at room temperature for two days; place in a covered airtight container. 4-6 months. Tips. 1  2-4 Days. 2-4 Months. But remember that cupcakes, like a lot of other sweets, usually have a best by date and not a use by date. Because of this distinction, you may safely use them to satisfy your sweet tooth even after the best-by date or best before date has lapsed. The problem with refrigerating cupcakes though is that the cake part dries out in the fridge. For a long-term option, you can freeze your cupcakes while preserving their taste if you use an air-tight freezer safe container. It is best to freeze them before frosting them, especially if the frosting includes any cream. The question is how to keep the cupcakes fresh. If it is only for a couple of days, then you are golden. Place in a plastic storage bag or container. Cupcakes keep best when stored in an airtight container on the kitchen counter. The Science Of Dry Cupcakes. However, if there are a lot of cupcakes and/or they need to keep for more than two days, then you have to do more than leave out on the kitchen counter. The first thought is to put in the refrigerator. That is not a good idea. Cupcakes stored in a refrigerator will dry out.  Refrigerator. Frosted or unfrosted cupcakes can be stored for as long as seven days in the refrigerator. They will be safe to eat, although the refrigerator can cause the cupcakes to dry out. Room Temperature. Most homemade cupcakes will be safe at room temperature for one to two days. To ensure freshness, store the cupcakes in a covered airtight container. If you do not have an airtight container, cover the cupcakes with several layers of plastic wrap. How long do cupcakes last? The shelf life of cupcakes depends on a variety of factors such as the best before date, the preparation method and how the cupcakes were stored. Cupcakes are enjoying a popularity surge lately due to TV shows like Cupcake Wars and multiple new stores specializing in just cupcakes. The problem with refrigerating cupcakes though is that the cake part dries out in the fridge. For a long-term option, you can freeze your cupcakes while preserving their taste if you use an air-tight freezer safe container. It is best to freeze them before frosting them, especially if the frosting includes any cream. How long will cupcakes stay fresh, and still taste really good and not at all stale??? How many days and at what temperature is best.  Wow! Other than advising your client to freeze them when she gets them, I'd be panicking. Cupcakes stay fresh for such a small amount of time, and if they were even a little over-baked, they are even more so doomed. I always bake cupcakes the day they are due (if the decorations are minimal) or the day before if they have more elaborate decorations. As to what stays freshest, I'd say sour cream chocolate. 
http://motherhood.modernmom.com/long-can-cupcakes-stored-after-baking-8386.html http://www.allthingscupcake.com/2009/05/11/cupcake-tip-1-keeping-cupcakes-fresh/ http://stilltasty.com/fooditems/index/17062 http://www.eatbydate.com/grains/baked-goods/how-long-do-cupcakes-last-shelf-life/ http://cupcakes.about.com/od/cupcake/fl/How-To-Keep-Cupcakes-Fresh-To-Eat-Later.htm http://motherhood.modernmom.com/long-can-cupcakes-stored-after-baking-8386.html http://www.eatbydate.com/grains/baked-goods/how-long-do-cupcakes-last-shelf-life/ https://answers.yahoo.com/question/index?qid=20110223132318AAMVmJS http://www.cakecentral.com/forum/t/663409/how-long-can-cupcakes-stay-fresh
how long do cupcakes stay fresh