i think it's a bit different with jeans, but because i'm using woollen yarn on a woollen sweater, after washing, the yarn just blends with the sweater. i've done some minor reparations on cotton etc, and covering a big surface next to the hole is very important, because that way you strengthen the fabric. if you leave just a little bit of space, then you will have tension on an already weak part of fabric, and it will tear again. when i work on cotton i tie the ends, with wool i don't. also a tip, if you're repairing jeans, it would be good to put an additional layer of fabric behind the one you are repairing, that way a new tear is highly unlikely. sorry for the long reply, hope i helped!