I ran 3 Mentors.  I wouldn't want a 4th.  I treated it as a turn 3+ play that would win the game the next turn.  I did play him early when the mana allowed (multiple moxen, sol ring, etc.).  I always wanted to be able to cast 2+ spells after it resolved.

I could see going to 4 if your meta is full of Lightning Bolt decks.  Also, if you aren't running a tertiary win-condition (my key-vault).  I just feel like I saw enough cards to do everything I wanted to in a timely manner.  There were a few games where I struggled to find the Mentor, but thanks to the heavy control elements, I was never in a precarious position.  Also, I really felt like the longer games favored my deck.  Dig through Time is so amazing in a long game.

However, my meta included zero shop decks.  That definitely influences my opinions. 

I played this list (with a couple of minor adjustments) to an undefeated record in a 20 man tournament this weekend. 

I loved how it works.  Mentor can kill out of nowhere.  I won quite a few games from an empty board by chaining Mentor, moxes/free spells, into Time Walk and attacking for 20+ the following turn with 3-4 tokens. 

I had to throw the deck together rather hastily, but I think these were the changes that I made:

-2 Treasure Cruise (deck legality is important!)
-1 Mental Misstep (I couldn't find my 4th)
+1 Dig Through Time (I want a 2nd now!)
+1 Ponder (felt like I needed another cheap draw spell to replace Treasure Cruise)
+1 Time Vault
+1 Voltaic Key (got cold feet and wanted another win-con)
-1 Misdirection (making room for vault/key)

When I run this again, I'm going to put in a 2nd Dig through Time and the 4th Mental Misstep for sure.  I'll probably be removing Vault/Key, as it wasn't really needed.  It was a great diversion tactic though.

Hi everyone.

My name is Eric and I live in Washington (state).

I've been playing vintage for a few years and we have a local league (similar to the VSL) that's been running for a while.

I usually play aggro/control strategies, ala Young Pyromaster control, or Oath.  I've been known to sleeve up dredge when sideboards get lazy

I also play on magic online to pass the time.

Glad to be part of the community.  Everyone have a great day!

-Eric