Were the liners de-glazed (Honed)? if they didn't do that, but fitted new rings the engines will drink oil. The new piston rings will never wear in to make an oil and gas tight seal against the liner, just skid over the top of the glassy glaze.
If they are using that much oil, then I would have thought that you would have a legal case against the people who did the work. The overhaul was not done to an acceptable standard, and they should either pay for it to be done properly by competent Engineers or do it themselves properly, ( if you trust them with your engines a second time)
It is always better to ask a stupid question than to do a stupid thing.