I would check-out what the Tuna fishers in So Cal are using. Latest is hollow core braid. Main advantage is that the mono-to-braid connection is much smoother, which can be an issue when going thru the guides. The mono top shot is required to have something the release clip can hang onto. Also some species of fish don't like to see braid.
Check out
http://www.charkbait.com/ for more info & pricing.
I have been using 20# power pro for Salmon for a little over 20 years now. According to charkbait it lasts least 12 years. When I re-spool I will go a bit heavier than 20 although I have never had a line break. With a 30ft 40# mono top shot I change it when frayed or yearly whichever comes first.
Best knot I have found is the GT knot: