I have an RCBS pot and normally let the alloy solidify.  The only reason I'd empty it is if making a major change to the lead/tin alloy mix for a different rifle or bullet.  But even then, most often, I change the alloy mix by either adding pure lead or tin to the partially filled pot.  To do so I keep tabs on the amount of alloy used & the mix ratio which makes it relatively easy to change the mix.  

BTW, I also have a high resolution lab grade scale & an alloy calculator (computer based software) that I use to determine the lead/tin allow mix if, for some reason, I have questions about the mix.

Wayne

9+1 ww/lino in Magdipper
Lino in LYman MM20
19+1 Pb/Sn in Lee 4-20
After done with a casting run on 
a pot/alloy, I flux, skim, add more
appropriate alloy to bring the pot up to
full, then Let them solidify in pot.
That way, next casting session, I can just
plug selected lead pot into PID, set casting 
temp for that alloy and then let to pot melt up and 
come to temp while I do something else like
going over the molds I will be using.
beltfed/arnie

Also let the lead solidify. I top up prior to turning off so is full to start and the mold sits evenly on the edge of the pot to preheat as the pot gets up to temp.

That PID controlled RCBS pot looks nice. If I did not all ready have a couple of Lee pots I would give it some serious consideration.

Too bad RCBS uses generic terms such as "thermostat control" and "temperature sensor" rather than telling the end user what might actually be going on. May not be PID & thermocouple, but they may be and the PID functions are set at the factory.

I have a new Lyman Mag 25 Digital to play with and it holds the set temp. extremely well and have been quite impressed with it.

JLouis

$109.99 for the new RCBS pot is a heck of a deal, especially so with a PID inside.  I see that MidwayUSA's regular price is $129.99 and RCBS lists the pot for $149.95.  I would jump all over that if I did not already have a PID.

I guess the casting equipment suppliers are finally starting to wake up to the use of digital technology.

Wayne

The Lyman Mag 25 furnace that JLouis mentioned also uses a PID with a very similar readout as the RCBS units.  So now there are 3 PID-based casting furnaces available.
Lyman Mag 25 (bottom pour & dipping)
RCBS ProMelt 2 (bottom pour & dipping)
RCBS Easy Melt (dipping only)

BTW, all hold 25 lbs of alloy.  No doubt there will be more offerings to come.  I bet Lee won't be left in the dust for long and Waage will have to upgrade their pot.

And how about Redding/SAECO and Hornady?  I'm surprised that SAECO never sold a casting furnace, at least not one that I remember. Didn't Hornady have a pot at one time?  If so it's not in their current offering.

Wayne