What do I say for a wedding vow?
That's a personal thing that you should make up on your own. It's not something that someone else can write for you. For examples you can search the web to get ideas of how others did theirs. In the end though, it means a lot more if they come from your heart and they have your own expeience and feelings in them.
There are books of wedding vows you can read. When I got married I was interested in reading vows from every tradition. You can choose to use whatever vows you like or write your own.
as long as you want to make them
most go for a few minutes but you can make them as long as you want
oooh well how long does the vows have to be?