I recently sealed a tub drain with with silicon 2 from a half used tube. This tube has been siting around for probably a couple years in a garage which was subject to freezing winter temps. I was, at first, happy to see that it was still flowing. I squirted out the first of it onto a piece of cardboard to get at stuff that hadn't been exposed to air and then sealed the drain. Now it is two days later and what I squirted onto the cardboard has not hardened. Should I redo this drain with a new tube?

did you put any on the bottom of the tub where the black rubber gasket is?
that is where any leak would show up.
you could do the top flange with nothing on it and as long as the bottom is tight it will not leak.

I did not add any to the rubber seal at the base of the tub. I put a ring around the lip of smaller piece that threads into the main assembly and tightened.

as I said, any leak occurring from under the flange on top follows the threads downward and is stopped by the rubber washer below.
fill the tub until the water runs down the overflow (maximum level) and let it drain.
if that doesn't make it leak, you are good to go.

I've been fooled by that too, old silicone looks good, but then won't cure after you apply it. I've started buying it in the smaller tubes so I have don't any laying around. I'm not sure what the shelf life actually is, but it's a fact that at some point it gets "too old."

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Not a plumber by trade but a fierce DIYer

$9 for a new tube. Cheap insurance.

I chaulk all the time but I am always having leftovers of white, clear, concrete, exterior, interior, anything. And I hate to waste. I'll eventually re-use in a few weeks of any of my leftovers.

But one trick I learned about a year ago has saved all of my unused ones...

I always have some plastic (sandwich bag type but not flimpsy) and some rubber bands. Quart size bags are nice and thick.. I use a corner of the bag and put it over the tip, leaving a slight gap from the tip to about an inch from the tip. I wrap the rubber band tightly an inch below the tip. I then push my chaulking gun and squeeze some silicon so it covers the tip and down to the inch. I'll squeeze with my fingertips after this to make sure it covers these areas.

That's it. The silicon will dry over the tip and below, essentially sealing it. When you want to re-use, simply pull this homemade plug and you'll get fresh silicon without it drying inside the tip and clogging it.

Works everytime and 50X better than a nail or screw to plug.