Yes, the print should last as long as you follow the Iron-on instructions. Also remember, not every iron is the same so you will want to test a pic on a small piece of scrap material to see if you need to leave the YOUR iron on longer or less time.
I washed them with the regular wash.
The only thing I can really suggest is if you want to try something like this, purchase a package of the iron-on stuff and try it on some scrap material first. Then wash it alone to see if it fades so it doesn't ruin any of your other clothing.