I'm in the same boat as you although my pool is not quit that old. I'm looking at a variable speed pump also as my electric bill is killing me!! From my research you will actaully want to run your pump longer but at a slower rpm so the water is turned over slower. I watched some youtube videos on the pumps and one of them said that if the rpm's are decreased by 1/2 the electrical usage is cut by 1/8! It almost sounds too good to be true. My problem is which brand to go with. I have all Pentair equipment now and their Intelliflow VS pump looks good but my local Leslies is really pushing the Hayward Eco Star. Both are the same price right now. I've posted a question on here to get some feedback on both so we'll see. Let me know what you end up doing and how it works for you. Good luck.