My guess is that the number of eyewitnesses were sufficient, since the Luke Gospel is consistent with the other 3 Gospels.

If there had been errors in his Gospel in 60AD, no doubt some eyewitness's around in 30AD who would have made comment.   

Previously all the Gospels were remote and I had relied on a priest to recite the stories of the bible on a Sunday and I accepted his intrepretation on how to use them.

This never satisfied my needs for my life.

This current process of examining Mark's gospel has allowed me to relate the gospels to my life and I have been enriched for the experience.

The messages are clear, very well set down and believable.

Thank you and God bless your work.