Originally Posted by OpieD
The question becomes, is there a way to check if the yeast is still going to be active when I add the priming sugar and bottle? Do I bottle and hope for the best in two weeks or add more yeast and see if the FG level dips some more?
Assuming your ferment is finished, and a 1.020 sounds about typical, although I might expect a 1.018...
Anyhow to do this, you could 'proof the yeast' Easy in theory, tough in practice. Basically take some of beer and mix with a bit of sugar. Wait a bit to see if you get any carbonation signs. When testing yeast from the store for things like bread (or rehydration for brewing, etc) generally you see some activity in about 1/2 hours or less. You also use like 1/2 cup or so of water, not much more. You can warm your beer to about body temp to speed things along for the test.
The 'hard part' of proofing yeast, it is can still be good, but you might never see signs of it being active - ie no bubbles, no foam, etc. Again, easy to set up, but also easy to miss what you are looking for.
ArcticBear is correct though, 55, heck as long as you didn't freeze, some yeast should have survived, even frozen, some might have survived.