"At this point, nothing about Shawna shocks me – at all," Keifer tells PEOPLE
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After being married for almost 16 years, Thompson Square‘s Shawna and Keifer Thompson say very little surprises them about each other. So when the pair recently played a round of “This or That,” none of their responses were considered a revelation.

“At this point, nothing about Shawna shocks me – at all,” Keifer, 39, tells PEOPLE. “Since we’ve been together so long. It’s like we pretty much know each other like the back of our hand,” adds Shawna, 36.

Not that either one is complaining about the predictability that comes along with marriage. In fact, they’re celebrating it.

To commemorate their upcoming wedding anniversary, the duo will soon head to Mexico for a little R&R. “We just never take time off or go on vacations,” says Keifer. “So, we’re actually going to force ourselves to go and have some fun.”

Though when the couple get back, they plan to get right into work mode. Currently polishing up their next album, which is due in the fall, the duo are challenging themselves to top what they’ve already got.

“I think we have an album now that we’ll soon be happy with,” says Keifer. “But we’re going to spend the next three months seeing if we can write anything that beats what that we have – just to make sure it’s the best it can be.”

The upcoming album’s first single "Trans Am" is currently climbing the charts.