Peter T - Yeah, that works with shapes that naturally displace without entraining bubbles. One suggestion I would impliment on your excellent mould is a pair of tapped holes in the flange so you can jack it apart later. Assemble it with the jackscrews + release agent applied to screws and threads so they are in place if needed.
I would also suggest a weep hole at the apex in both sides of the mould with a threaded plug and filled with wax to the component level so that you can remove the plug, the wax and then introduce compressed air (or even hydraulic pressure / plugscrew against soft wax) to push the part out of the female mould or off the male counterpart. I see you have holes there but I can't see if they go through.
In most cases once it has "cracked" loose, the rest is easy. Easier to provide it up front rather than after you have a stuck mould on your hands.
petertha - all resins have shelf life issues. Polyurethanes need to be kept warm - like 30°C - I keep mine in a hot box - even so shelf life is seldom more than a year. Below 10°C urethane resins start to separate into constituent parts and have to be "reconstituted" by heating and blending (at 40-50°C) simple blending creates the illusion of reconstitution but results are poor.
Epoxies on the other hand like to be kept cool.
With soft urethanes, cleaning out is simple - so long as you let it cure properly before stripping. Hard urethanes you need to keep an eye on your residue and when it reaches the consistency of toffee, strip the feeder chamber and pipes - not the mould itself - leave that until it is well cured.
It even pulls out of the tubes (as long as you ran release agent through them) otherwise the tubes are "consumable".
Thanks for "bubble gods" - will mentally file that alongside "shop monster" which gobbles up any small part dropped on the floor.
Above my truck oil filter vaccuum pot - I made a lid with a window and illuminating LED's so I can keep an eye on degassing resisns prior to gravity pours etc. The black "seal" in the lid is gravity poured soft polyurethane and pigment - no release agent used in the groove.
Regards, Ken