I'm sure this is true. However one thing in the back of my mind when discussing/reading bank life discussions is - does it matter?
At the end of the day batteries, especially lead acids are actually pretty cheap compared to everything else on a boat. If for space or weight reasons you don't want to add batteries it's not unreasonable in my opinion to decide that you'll just replace them every 2 or 3 years.
Personally I expect to get plenty of life out of my batteries and put a lot of thought into my system. But with $120 of batteries compared to ~4k fixed yearly expenses plus maintenance and discretionary it's not going to matter a lot in the big picture.
This is actually pretty true depending upon what and how you use the boat. I'm 28' on deck, just a skoosh under 30', the OP's boat is from the same era
but a foot or so longer......reality is, for how I use my boat, electronics on it, a single 85ahr batter worked fine! I can get upwards of 24-36 hrs of power out of it. Then again, all I am powering is house lights, running lights and some ST60+ instruments and radio. One does not need a lot of power to do this. Now if you are running GPS, chart plotter, fridge plus a few other things ON TOP of some of the basics if you will on a boat, then yes, one needs more wt in battery pack to function at a reasonable length of time.
Once you get to the a single 12V or two is too small, then as noted by some, 2 6V lead cells frankly is the best bang for the buck/wt ratio to supply your power needs. This is true from land yacht experience, along with water yacht experience.
For either application, it does no one any good to have as in the OP's case 2 150lb batteries, if he only needs a single 12V 65-100 lbs one to serve his needs. At the end of the day, one needs to decide battery sizing based on ones OWN needs, not mine, nor mainsails, nor smackies, CD's etc.