First GF Beer - Looooong Fermentation

I brewed a GF beer for my wife about 10 days ago - steeped GF oats, sorghum syrup (briess), D-45, buckwheat honey, maltodextrin, rice solids and lots of hops. 5 Gallon batch with an OG of 1.064 so I pitched two packets of US-05. It's been parked in my closet at around 65 degrees. Here's the thing...it's been 10 days, and it's still active. Two days ago it was still at 6-7 bubbles per minute, today it's down to 1-2 per minute. I've brewed a lot of ales, but never one that took this long (except a saison...but 3724 is finicky).

I'm not worried about the beer, it'll be done when it's good and ready to be done - but has anyone else had this long of a fermentation with a GF beer? Is it the complex sugars in the honey/malto/d-45 that cause it to take so long?

Anyway

Yes, we've all heard of it. Yeast nutrient, whirlfloc, and gypsum all seem to cut down ferm times, but 10 days is really not too long for GF. Some of my beers finish in 4 days, but most of the time I let them sit at least two weeks anyway just to make sure the yeast has had time to clean up after itself.

I used nutrient and Whirlfloc. No gypsum in this one - didn't have any on hand. Luckily I'm a patient brewer.

Well, patience does kinda come with the territory . Seriously, though--have you actually checked the gravity? Airlock activity is no substitute for gravity readings, and that's the only way to reliably tell when fermentation is complete. In any case, at 1-2 bubbles per minute, I would strongly suspect fermentation is complete, and you're just seeing release of CO2 from solution. Has the krausen fallen and is the beer beginning to clear?

I usually ferment at 68°F, occasionally up to the low 70s (Stone ferments all their ales at 72°F, FWIW, so I know fermentation at that temperature is just fine), and my beers usually finish main activity in a week. 65°F I might expect to slow things down a touch, maybe.

Also, what was your exact recipe? If you used a lot of honey, that also can slow things down a bit.

Here's the exact recipe:

Batch Size: 5 Gallons
OG: 1.064
Yeast: 2 packets US-05, no starter

Fermentables:
1 lb. Toasted GF Oats, steeped from 150 - 170 degrees (~25 min)
1.5 lbs. Briess Sorghum Syrup (60 min)
1 lb. Rice Solids (60 min)
1.8 lbs Briess Sorghum Syrup (30 min)
1.5 lbs. Buckwheat Honey (15 min)
1 lb. D-45 (15 min)
1 lb. Maltodextrin (10 min)

1/2 tsp. yeast nutrient (10 min)
1 whirlfloc tablet (15 min)

Hops:
1 oz Centennial (8.7%AA) 60 min
1 oz Cascade (6.2%AA) 30 min
.5 oz Citra (14.1%AA) 15 min
.5 oz Summit (17.6%AA) 10 min
.5 oz Citra (14.1%AA) 5 min
.5 oz Summit (17.6%AA) 3 min

Dry hopping with 1 oz cascade and 1 oz citra for 7 days.

It might be done. It might not. The airlock could be going because of fermentation, or because the barometric pressure is rising, or the temperature is rising a bit.

If you take an SG reading, then you'll know if it's done. Or not.

Like I mentioned in another thread, I was doing a version of igliashon's no nonsense GF stout, and after two weeks I still had airlock activity (consistently). After taking a reading, I decided it must have been CO2 coming out of solution or something else (like Yooper mentioned) because the beer was most certainly done.

I have had several beers take that long to finish, cut a corner once in the beginning and bottled it only to have bottle bombs. Second (or third) the gravity readings, or just wait for the airlock to stop completely.

Airlock activity does not indicate fermentation. I have a beer that is still going after 2 weeks at 65F. Almost no airlock movement. Bottle bombs suck. Take your time and it will finish eventually.

A somewhat related question - is it normal to have a longer lag time? Did my first sorghum extract beer yesterday and no visible signs 12 hours after pitching rehydrated Safale 05. I used a Whirlfloc tab but no nutrient. I still need to measure to see if it's actually fermenting and just not showing it but I thought I'd do some research and give it a bit longer in the process. Also I'm trying some active temp control for the first time (swamp cooler) so I'm attempting to start fermentation at a cooler temp than usual, so that may very well be the culprit too.

Edit: I measured again ~12 hrs later and it wasn't fermenting. I pitched a new packet along with some yeast nutrient.