almost 3 years ago - anonglitch - Direct link
Hey @EnchantedGilda

Upgrading the Training Grounds will help you train Units like Cerberus or Banshees a lot faster. If you participate in the Tournaments, and the Spire, the faster you train your Units, the better!

Especially when they change their shape/size/orientation, their training speed jumps forward significantly; you will love it!  
almost 3 years ago - Herodite - Direct link
Hi @EnchantedGilda I think this is totally down to individual gameplay. The only benefit you will see from this point on is Training Speed, as you've already unlocked all available slots. Personally I can't help but upgrade as I like the ever changing building :D

Again this is totally down to you. If you feel you're progressing well without the need to upgrade. Then that's fine!