For the most part, I like to take the time.
I find the art of the envelope to be quite a relaxing way to spend an evening, and find that making this time a regular part of my sweepstaking helps to keep my spirits up and avoid the "sweepstakes burnout" that some can fall into. It's like sending sending a dose of good cheer out into the world. I sometimes think about all the hands it may pass through on it's journey, and it's a happy feeling to share these little mini works of art with postal people and others I most likely will never meet. Strange, but true.
Generally, though I don't care to spend an inordinant amount of time on each envelope, I do, at times, like to create a theme of sorts. I prefer to have each envelope be unique so it is its own work of art. Sometimes a theme can be arranged around the postage stamp itself. It may be colors, using purple ink for a stamped design, along with a purple return address label, and purple postage stamps. When the Hershey's Kisses stamps came out I did some work in red, with hearts drawn in colored pencils or mini "love" stamps. Springtime brings flowers and butterflies, summer heat prods bright oranges and yellows, fall starts to cool things down a bit with more muted tones, and winter is a whole story in itself.
Occasionally a particular sweepstakes will warrant its own personal design. Hot chili pepper postage stamps with a sombrero etched on the back for a trip to Cancun, for example. It sets the mood for a winning moment, even if there is no prize immediately involved... Because in the end, as we all know, it's all about the journey.