Not sure what to make of this. I guess you can ramp to 8 mana on the 6 mana turn, but other than the combo that everyone loves, Songhai doesn’t have any notable plays on 8.
Even in the combo deck, your opponent can anticipate when the Songhai player is gaining the extra mana and play some sort of heal/spell prevention on that turn.
You have a 4 turn window to play these before the effect becomes useless, and only 2 of those turns are available unless you ramp this out.