lao po ,it doesn't mean his wife is old ,nowadays many young Chinese men ,even he doesn't get married with his girlfriend,but they always keep good relationship,he also will call his girlfriend "lao po". In China ,most of couple ,husband call his wife "lao po", lao po call her husband "lao gong".
“太太”,maybe shows that you are very gentlemanly. you and your wife go to a party ,then you introduce your wife to your friends ,you can say "zhe shi wo tai tai ".
generally speaking,most young men ,they don't call his wife "太太'' in China.
maybe in Taiwan and hong Kong "太太” is still used widely.