Butterflies are delicate.  It is an inherent quality of the insect but with proper care you case can last indefinitely. Here are the simple precautions and care to make sure your case lasts a lifetime:

1.  No direct sunlight - it is only natural to want to put these beautiful butterflies near a window to light the sunlight reflect off of the wings.  This is a bad idea.  Just as Direct sunlight fades your couch,  curtains, carpet, flooring, car interior, and so on, it can also fade your butterflies.  Fading can occur after 6 months of direct and continuous exposure to sun light. Once in a while is fine but continuous exposure will ruin the color.

2.  Don't drop it - the cases are actually very strong.  dropping the case may only result in chipping a corner of the case but it will do very little damage to the case.  However, it is likely destroy the butterfly inside.  the butterflies are desiccated and are very fragile.  Once dropped the specimens inside are a good as dust. This is not to say that cases cannot be handled, they can, one must just use proper care when doing so.  These cases are works of art and if treated as such will last indefinitely.

3.  Never use ammonia based cleaners.

How to care for your case:

1. Dusting - just like any other surface in your house, your case may require some periodic dusting. It is best to use a clean 100% cotton cloth (like a t-shirt) to clean off any accumulated dust.

2. Cleaning solution - the best cleaning solution for acrylic is Brillianize.  this product is available from any plastics supply company or it can be ordered online. Just follow the instructions on the label. Again, use a clean 100% cotton cloth (like a t-shirt) to clean.

That's it, pretty simple.