The best way is to make multiple copies on multiple storage mediums and regularly check for any data degradation. There is no one single format that will last long term. Everything has a chance of failure for an infinite number of reasons.
You only need to store one TB, just buy a pair of 2TB hard drives, check the data yearly, and then whenever the warranty expires buy some new drives and copy the data over. That's about as simple and safe as it'll be for you.
Either pay a cloud storage provider about $4/month to hold it for you, or buy a couple external drives and verify your backups yourself about once a year then replace drives as they eventually fail.
I figure the break even point is about two and a half years. If you're committed to hoarding your content for longer than that, buy storage drives. If not, rent cloud storage. If your drives die in less than that you would have been better with cloud storage, but that isn't likely.