I have been monitoring this stock for while for an edge to the INDU/SPX. Back in Jan 2017 I was expecting at least a new high for wave [v] to end wave 3.
Fast forward, not only has BRK.B made a new high for wave [v] of 3, it's also pushed above the fibbo target for wave 3 where wave 3 = wave 1 x 1.618, which is a common target for a 3rd wave of an impulse wave. I think the bulls now want to tread carefully, if wave 3 is close to ending we can expect a decent pullback soon for wave 4. Any pullback for wave 4 should also align with a pullback on the SPX/INDU.
Short term, I would like to see a minor new high to then make a clear 5 wave move for wave [v] of 3. Its then I think the bulls may want to think about taking some profits off the table, as if I correct we can expect a substantial pullback for wave 4 towards the 160.00 - 165.00 area.
I am targeting a move towards 19500 on the INDU and 2200-30 on the SPX for their respective wave  corrections, so that should see a pullback to around the 160.00 - 165.00 area for BRK.B for its wave 4 correction.