Seems excessive and you're bound to find spoilers all over the Internet regardless. Best solution to avoid them is to not seek out content related to what you're trying to keep unknown and this applies to all things not just RimWorld.
As we've kind of reached a stalemate here, I think 2 months is a fair compromise. It's 3 against three in votes, but a lot of votes in favour of 0 days in the comments, 2 people pro 6 months and 2 against.