I did not buy an extended warranty for a few reasons.
First, I had a problem with intermittent shut off and restart, like a few other people on this forum.
I contacted Sharp and they said that the problem was registered and if it ever gets worse, they would fix it.
That means no need to get the warranty extended for the most common problem. It hasn't had the problem in many months.
Second, warranties are sold for profit and I would rather keep the money to buy the next generation of set when this one wears out.
I would say that you could sit as close as 6 feet (2 meters) from the set without seeing the pixels and compression artifacts from source materials.
I sit more like 10 feet from the set. The closer you get, the more viewing angle becomes critical, of course. Up/down is not bad, but side to side is sensitive to angle...