I've done my own digging on free dating sites for married couples and come up short. For married in particular, most of the disappointment traces back to the number of live users. The ratio of matches to conversations matters more than whatever the landing page promises, in my experience, which is the whole problem with married couples.
Every time married comes up, you get further if you use a photo that appears nowhere else online. With married sites, half the frustration disappears once you keep a note of what you actually spent. Look closely at couples sites and the practical move is to ask a specific question in the first message.
Same story on married: the depth of the profile fields is the number worth watching, not how many photos people post. Most threads about free dating sites for married couples miss this — nothing improves until you report problems early instead of blocking quietly. What has actually worked for you on couples sites, and what would you avoid?