I think the number isn't important, if you have 1000 and every single one points to a relevant point, close to what they were trying to find- then there is absolutely no problem!
Just watch they don't all go to the homepage or are trying to use them to an SEO advantage etc; thats not what they're for and you will get penalised for that.
I've just done about 100 on a client's store recently and after a couple of weeks their rankings improved incredibly! they were getting hit with so many 404s etc