For me tower spawn is a must if you manage to capture the tower (capturing the tower is a must too, if you have a secure hold over the tower you've almost won). I usually have a few Speartons and lots of archers when tower spawn comes rolling around (if my opponent plays super defensive I get spawn even before spears) and archers with fire arrows+tower spawn allows for massive harassing of the economy and of the army. It's much better than sending your own speartons in since you don't have to retreat it or worry about it dying, just hit and run with the archers, then kite back to the tower. I don't think I've played a single game where I haven't gotten the tower spawn--if I have the tower, that is.