Attacking or saving shield?

I didn't mean to say you shouldn't keep them all busy. But it's good to try to plan them out so you don't have multiple days before one finishes. If you've got three builders that won't be done for 2d, upgrade an 18 hour collector or something if you can. I'm keeping one open now myself but only because I don't have anything left but collectors to upgrade.

Thought of another tip:

• If you only have a few minutes left on an upgrade and you have to log off, consider hurrying it with gems