I don't think Black's 29th was a waste of time at all. In fact, I think it was a good idea (that being to get the knight into play, not to start a pawn storm). Given a bit more time, Black might've tried 32... Qd8. This forces 33 Nxe3 and after 33... de 34 Qxb7 Rc7 35 Qb6 Ng3+ wins the exchange (36 hg hg 37 Kg1 Qh4 38 Rfc1 Qh2+ 39 Kf1 Qh1+ 40 Ke2 Qxg2+ 41 Kxe3 Qf2#). 34 Rfe1 would be a better try for White, but I still have the feeling that Black is getting good play here.  Also (as the game went) 33... Nf4 would've left him with a nice position.