At work, I put a 3d ABS part printed via 3d hubs (5*20*30), in the chamber at 1 mbar. No signs of breakage what so ever. No signs of sudden leaks.
Going anywhere below 1mbar, i.e., to 10^-infinity mbar, I think should theoretically still not cause any breakage or sudden leaks, as the expected mechanism of failure depends on the pressure difference; i.e., [1atm-1mbar] ~=[1atm-10^-infinity mbar].
Based on the above I have made some more parts to be put in a chamber at 1E-5 mbar.