There is certainly no doubt that the closer to your age another couple is, the more common shared interests you will have. Also the higher your chances of goals for your activity together to be similar. Too many years separating folks can certainly diminish any attraction that may have been the basis for contact. Must admit, the prospect of a more mature (older) couple for our first experience in the lifestyle held appeal to both of us. We for some reason surmised no one older could possibly be inexperienced (not true, no apprenticeship or journeyman regimen exists) and since all come in their own time, for their own reasons, you just never know. But we were fortunate, they were not the newbies we were, and they were WAY more comfortable with the prospect, the activity, and it was a good experience for us. Without unexpected jealousies, uncomfortable glares between them, and they were gracious hosts at their home, sharing their pool, hot tub and home with the ease we had hoped for. They remained friends, socially, and although we did attend parties where they were also present, the encounter was not repeated.
I realize now how brave they must have been to take on such greenhorns - certainly not something we would seek to do. It would be nice to provide others with such a nice first experience, and yes, have done so in the past. But really don't like the prospect of that any longer. Too many variables that can go wrong, and just don't like the upheaval.
I am sure that you both, like most, can get along quite well socially with folks of all ages. Probably have even enjoyed a night out with the folks on occasion. As we have with our kids, who are grown and married, with families of their own. Would I want to get naked with those of their age group? Not only no - but hell no. Nor would I really want to with those in my folks age group (which is WAY up the ladder from the ages you mention). Since you are both at the young end of the spectrum, don't think there exists too much possibility of those who are too very much younger. I wouldn't set an "age limit" in concrete but a general vicinity boundary, defined more by common interests, goals, and shared activity interests is probably a good yardstick.
Since we no longer have kids at home, we don't desire those whose time and activity is dictated by young ones still in the nest. We like blues clubs, concerts, clubs with live bands - but really don't desire listening to rap, hip-hop, or jazz even - as we find all to be non-melodic and irritating for the most part. We don't want folks who need to take medications to make their body parts work - or medications that keep the excitment level from being too hazardous on their hearts. We don't enjoy those who find a need to knock the edge off their nerves with liquor or 420 in amounts that cause doubt about functionability, or a recognition next time we meet. These are parameters that are more important to us than numbers. We have known some very young older folks, and some very old younger folks. Prefer those with open minds, wit, humor and a zest for life. An ability to converse on more than three lettered topics, for longer than three minute conversations. An acceptance of themselves and others for the values that matter most. Seek those whose company you both enjoy, and all the rest will come easily.