sts

How is the consonant combination "sts" (frosts, inquests etc) pronounced in normal, reasonably fast conversational speech?

In careful speech it's /sts/ but in fast speech it will be /ss/ or /s/.

At least here it is actually realized as [sʲtʲsʲ] in careful speech and [sʲː] (not [sː] as if it were /ss/) in fast speech.

[sts] is easy to pronounce [s] (as in city) + [ts] (as in pizza)
one can argue there are only 2 consonants there s [s] + ts [c]

The [ts] or [tʲsʲ] properly speaking is realized as an affricate, but it is underlying two different phonemes, /ts/, unlike in, say, Italian or German.

Hi I am a native speaker and I always have trouble pronouncing this right... Is that weird or what? I don't notice when I'm talking quickly but if I try and consciously pronounce it right it just sounds wrong..

So it's kind of like a long double s sound. Are there any other instances of this in English?

Forests, lists, fists, Christ's, hosts, etc.