Pay Dirt Photo illustration by Slate. Photo by Liubomyr Vorona/iStock/Getty Images Plus.  Our advice columnists have heard it all over the years—so we’re diving into the Pay Dirt archives to share classic letters with our readers.  Submit your own questions about money here . (It’s anonymous!)  Dear Pay Dirt, My partner and I have been together for eight years. We are committed to each other, but neither of us wants to get married. We keep our finances separate and pay housing expenses based on a ratio of who makes more. When we moved in together and decided on this split, I made significantly more than my partner and paid a higher percentage (60/40). Over the past few years, I have gotten normal raises (think the regular 3 percent to 5 percent) and I thought she did, too, as she never said anything different. I got two big bonuses over the past few years and disclosed them both to her, and she has disclosed her bonuses to me.…