Definitely spread them out among accounts but I agree with the consensus here of about 10-15. A good rule of thumb is to think like a "real" user. The average Joe/Jane is going to upload, maybe 1 video per day. Google knows this and will flag anything it sees as "unusual". Ideally, you might have 20 accounts, for example, and upload one per day, per account. It really depends on what you're doing, though. I think Google will let you slide if you consistently upload, say, 15 vids a day per account. <---that's just a guess. But, based on personal experience, I've uploaded about 20 vids daily on one account and never had an issue.
Also keep in mind that the main reason accounts get banned is because they get flagged. As much as we like to speculate, YT doesn't really monitor our accounts. They rely on people flagging them for duplicate/copyrighted content (beyond their obvious content catching system when you initially upload).
Good luck, man!