I have no real use for builders in VV1 or VV2 either once all the puzzles are all done. As others have mentioned they can be trained to become Elders or possibly Jack of all Trades, but I (in the couple of games I've played so far) tend to give the villagers a rest once all the puzzles have been solved and all levels of tech have been achieved. I reckon that the builders carried out a Herculean task in carrying out the restoration of the statue, and deserve to take time out. I'll therefore train a few villagers in Medicine and the others in Farming, with, of course, a few females in Parenting to carry on the tribe. Existing builders/scientists I'll give a little retraining in their new career, but I won't bother them overmuch.
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To err is human; to arr is pirate.