Nothing mid-life crisis about it! We both go off on short solo holidays as much as logistics allow (usually two-to-three times a year, each, slotted around a couple trips a year together). In fact, Mr Seahorse is off to St Leonard's next Friday, because it's his turn to vacate the flat (I did Whitstable in January), and I cannot wait.
There are few things more blissful than being entirely alone, in your own head, in a new place. Enjoy it. And be sure to return the favour for your wife!