Any decent kite repairs will be stronger than the original kite in that spot, the question is, why did the kite need repairs? They may not shorten it's life, but if it is old and worn it may be running out of life anyway.
If, however, some idiot like GreenPat muffed a self launch and draped it over something sharp and put a slice in it then there's nothing to worry about.
I would say to you though, if this is your first kite then you're on a winner. Most people give their first kites a hiding and they generally have pretty short lives anyway. If you save a couple of hundred dollars on it and put it towards your second kite you'll get much better value for money. This may seem obvious in hindsight but the lure of new and sparkly can often overtake responsible purchasing. You will be putting it in the water and on the sand a lot at first, and it will wear faster than the next one, that's just a universal truth.
I'm on kite number six now

(not counting a trainer which I bought, for some reason,
after the first three LEIs). Worth every cent.