I have to say, Dumbledore really lets his hair go in five to seven years. In the Riddle at the orphangan scene he has shoulder lenght dark hair with a small beard, but in the Chamber of Secrets flashback, both hair and beard are long and grey. I think the young Riddle is supposed to be about eight (maybe five at the youngest) and around 15 or 16 during the flashback, so maybe 10 years max.
I'd would love to do a freeze frame on the bottles of memories to see if we could read all the labels. Seems they are doing the Pensieve a bit differently than before. I really wished they would have used it in OoTP per the book instead of Harry breaking through Snapes defenses.