I think, running your batteries down to 40% occasionly is fine too, since you only boondock a few times a year.
Some of us boondock most of the time and others full time. I am full time off grid on my boat and try to boondock for the few months a year I RV. If I ran my batteries down to 30 or 40%, every night, they would probably last a year, if that.
I haven`t read Handy Bob in a while, but all the sources I have read, strongly recomend not going below 50% state of charge. The happy place with the least amount of generator time is between 60% and 80%. Charging beyond 80% is a lots of energy for a small gain.
My Sam`s Club batteries lasted 5 years for 1300 cycles, before they lost 75% of their capacity. Sure beats the electric bill.