I use Namecheap, and I have deliberately avoided their auto-renewal service because it doesn't offer me anything.

The key point is that a human needs to be involved in an audit process which occurs regularly. And so I renew all my domains once per year in December, a year in advance.

Now that I think about it, I suppose I could extend one year at a time, but keep a 1-2 year buffer (or larger) in case of dire emergency instead of a 0-1 year buffer.