I planted one about 5 years ago and I cannot recall ever doing a thing to it. These things seem to be "the" plant for roadside and median plants. When the drought a few years ago killed or damaged many roadside plantings such as viburnums and dogwood shrubs the burning bushes did not seem to mind. If you really wanted to I suspect you could trim them anytime of year but they have a nice natural shape. Even the cultivar 'compactus' will get pretty big.

I will point out that burning bush (Euonymus alatus) is on the list of invasive plants for Virginia. Below is a link to the document.

- Brent

Here is a link that might be useful: Invasive Alien Plant Species of Virginia