Generally speaking, yes. You want to do the full thing. The back half of the event is where most of the rewards are. It's heavily weighted towards to end. Part way is only really recommended when you only need the first few to complete someone.

The goal is to spend in other events to maximize the amount of rewards you get all at once.

But as others already mentioned, yeah sometimes the cycle is bad so it's difficult to say "always do it" but usually it's a good idea. Esp. if you are F2P only.