"Our sex life feels healthy and natural, even though it doesn't measure up to popular statistics. "

I forgot to mention...if you are comparing your sex life to "statistics" that is not the path to relationship happiness. Sex is a unique dynamic for every couple. And lots of people lie when participating in sex surveys...for example men tend to exaggerate their total # of partners. Anyway, you need to figure out what you want and whether it correlates with what your wife wants. Leave statistics out of it. I think it's natural for a marriage to go through bumpy spells...it's all about whether you want to put the work in to get through those spells or whether you feel the differences cannot be resolved. Only you can decide that. Initially, you mentioned lots of great factors in your marriage. That's a great start, right?