I am working in the US (since 2001) and my wife has retired although not drawing a pension yet. I am able to make Class 2 NI contributions and she makes the higher cost Class 3 contributions. Back in 2018, because we were missing NI contributions, we each made a single payment to cover the years 2006-2018 and so now are eligible for a much larger UK state pension. Definitely worth doing IMHO.