Penny Lancaster has gushed that her husband Rod Stewart is "so youthful, he's a machine". "You can't stop him. He's the one that says, 'We're going out tomorrow night' or, 'Should we go to Paris this weekend?' I'm like, 'We were out last night!' he has ideas about how he'll wind down but he'll never stop. "We're already looking at tours next year and the year beyond." The former model and TV personality opened up about their relationship in an interview with Saga magazine, in which she also revealed that the Maggie May hitmaker has promised to stick around with her for "another 20 years". Lancaster has been married to the rocker, who turned 80 in January this year, for 18 years, but says she had to convince his six children that she wasn't a gold digger when they first met. Stewart already had two marriages behind him when they met, and had six children by four women. "They were, 'What's her angle?' I was just... 'I like the guy!' Whatever decisions Rod made with exes, I was always very inclusive with them, making sure they didn't see me as a threat." Lancaster and Stewart later welcomed two sons of their own - Alastair, 19, and Aiden, 14.