You are correct that many women experience light or no periods at all on the Mirena after the initial adjustment period. However, you should be aware that it is common to experience irregular bleeding/staining for the first 3-6 months on the Mirena as you adjust to the hormones. We recommend reviewing the laws of staining, since not all staining will render a woman niddah nor invalidate the clean days.
If you do find that extended tehorah periods are affecting your relationship without the cycles of anticipation and excitement caused by niddah, you and your husband should brainstorm ideas how to keep your marriage fresh: periodic date nights, surprise gifts or activities, experimenting in intimacy, etc. There are many ways to bring a new spark into your marriage and you should try to find new and varied ways that work for the two of you. Kol hakavod for working at your marriage and not taking it for granted.
Please feel free to get back to us with any further questions.
B’Hatzlacha!