What level should I stop upgrading tower health?

I am running a defensive build. Got my defense % to level 25, maxed out my orb labs. Just about to finish up all of the golden tower and black hole labs. Was planning on adding a few perk labs to help my overnight runs and then start working on my death wave labs (haven’t started any of these yet). My GT, BH and DW synced at 3 minutes. My question is when to stop upgrading health labs or should I take it to max? Thank you!

I am running a defensive build. Got my defense % to level 25, maxed out my orb labs. Just about to finish up all of the golden tower and black hole labs. Was planning on adding a few perk labs to help my overnight runs and then start working on my death wave labs (haven’t started any of these yet). My GT, BH and DW synced at 3 minutes. My question is when to stop upgrading health labs or should I take it to max? Thank you!