My team has a local vendor screen print our numbers, and they last years (I think the longest was 5 years, and they still looked good when the robot got relegated to the scrap heap)!
I blame gift bags.
Most kids today never learn how to wrap a present. If you can (neatly) wrap a present and use a staple gun, you can figure out how to put fabric on a bumper.
Perfect! Now I can market another robotics skill as applicable to life – learn to make bumpers, extend that skill to wrapping presents!
That is EXACTLY why my team Moms head the marketing and bumper making subteam!
/offtopic
Speaking of gift bags… I was at a local training event last weekend (JUMPSTART at St. Cloud State University). All of the students got gift bags. At the welcome speech, one of the speakers told them to look in the bag for something specific. The sound of 500 students all opening plastic bags at the same time in an otherwise silent room was really freaking cool.
So don’t knock gift bags 
At the risk of Dana calling me a team mom…
I help make the skins and bumpers for Lights Out. I bought a Silhouette Cameo 3 (thank you Kelli) and it is robot life-changing. I used shiny vinyl sticker material (the outdoor kind) not iron-on for the skins and bumper numbers. They were pretty robust - I cut several sets and brought them to competitions in case a number needed to be replaced, but never did. After 3 off-season events, the numbers still look pretty good.
Now I’m using the machine to make a Christmas village, so mom confirmed…
~Meredith
Thank you for the compliment! We are lucky to have a student on our team whose family has a graphics business. She is also fully trained in the equipment and was able to add the numbers to our fabric.
This student took our vector 78 numbers (in Adobe Illustrator .ai format) and then converted them to vinyl heat transfer decals.
Here’s a shot of the bumpers on the field from last year: https://www.instagram.com/p/BTYvkt6F8h8/?taken-by=airstrike78
And a close up: https://www.instagram.com/p/BRMyuHBFgUa/?taken-by=airstrike78
Shoulda posted pictures of the Christmas Village too.