FLR(M) expiration: which visa do I need next?

[shhh]

I'm confused! I'm on the FLR(M) visa, the spouse of a British citizen. I work permanent/full time. We don't have any children. I entered the UK on Tier-1 in 2009. I need to renew my visa, but I'm not sure which one I need. We're staying in the UK for another 5-10 years, so the FLR(FP) seems right, rather than SET(M), but I'm not sure. Which do I need?

[Amber]

If you've spent two years on FLR(M) then it's SET(M). Look at yourself staying in the UK permanently rather than for a fixed period. When you've settled you can, at first sight, apply for citizenship (to naturalise).

[shhh]

Okay! SET(M) is way more expensive than FLR(FP), but it's better in the long run? Also, I'm an American citizen and don't ever see myself needing to naturalise...

[Amber]

You should naturalise as you're allowed dual citizenship, settlement expires if you leave the UK for more than two years, citizenship doesn't. I'd get it whilst you can.