I like to get them into their pots as soon as the roots start to show. Snapping and kinking roots at this stage can significantly slow things down. I don't bother transplanting them from small pots into large pots, IMO its better to put them straight into the pot they will be flowering in. You might need to use a clear plastic container to cover them to keep in humidity for a week or so, but I use an anti wilt spray that negates the need for high humidity. If my main room was still in veg, I would just have my tray of clones sitting on the floor until they were ready to be potted.