To be honest I haven't had any real issues yet, my moulds are still ok, but I do notice how tight the parts are in the mould. Rich, when you demould hot do you get very bad print-through? 

No issues with print through. Once the moulds have been post cured and ready to use, they should be nice and hard. Luckily I only have to cure at 72 degrees C so the moulds are more warm than really hot.  I think if there is going to be a print through issue it would happen regardless of de-moulding hot or cold. The worst mould section for me is the fuel tank top, It has a good compound curve shape so is best removed hot to help stop it shrinking onto the top of the tank. BUT it also has a thick square edged filler cap neck that is prone to being chipped on the edge so I have to use the extraction bolt to lift it a little then let it go completely cold to let the neck shrink back. That it the only problem I really get with wet laid glass moulds.  The carbon tooling I can leave to go stone cold and not have any issue with expansion or shrinkage as it heats up or cools.