First there is no reason to check it "frequently". Just let your beer sit in primary 3 weeks (my preference) then check it. Wait 3 days and check again. If they are the same (temp corrected) its good to bottle/keg.
Big beers can take longer and also take longer to carb.
Dont worry about...
I normally go about 3-4 weeks in primary before bottling but due to life getting in the way my German Alt went 8 weeks and turned out fantastic.
Today I finally bottled a NB Winter Warmer I brewed on 12-4-13 (10 weeks ago).
The warm flat beer tasted very good and I will test a few in 3 weeks or...
How long would they be stored in there? How much headspace?
You will want to keep headspace to a minimum since there will most likely not be a CO2 layer to protect it. A carboy would probably be better for long term unless you can inject some CO2 in your bucket/tub.
I have left beer in my...
primary fermentation is probably done already. the bubbles you see are from pressure change as it warms up. Just let beer sit in the primary so the yeasties can clean up and settle out. I usually leave mine in primary for 3-4 weeks unless it needs aging or life gets in the way.
The longer the beer is in primary the firmer the yeast cake will compact making it easier to rake to bottling bucket without transferring the "sludge". I have not used a secondary and I usually go 3-4 weeks in primary unless life gets in the way..... I gotta get that batch bottled I brewed on...