Thinking Ahead- If you tried everything to seal leak and nothing works
How long will it take before the Rear Main Seal goes out?
Would it be wise to drive on highway? Any thoughts
would be helpful. 
It’s possible for a rear main seal to fail catastrophically by either becoming dislodged or from a piece of the seal breaking off. This can lead to massive oil loss and engine destruction if the engine is not shut off immediately. (That’s what the red oil light means; stop now.)
However, the odds of either one are very, very slim and it’s really not something that I would worry about. Usually a rear main just leaks oil progressively worse over time and may get to the point where it’s a steady drip.
Thank you for your thoughts. I will try not to worry about it.