Thanks for the info.I read somewhere that couple of experienced programmers can create a 3d engine from scratch within two months. Hope that answers your question. But the for starters it maky take longer. Basically if the objective of a 3d engine is to only create a 3d pong, then begineers can make it in 3-4 weeks.
When testing the capabilities of the engine, i'll recreate most games but there's a game i want to make that's why i'm making the engine.