Well, you can use anything you want. It's your pool

But for accurate measures there's the k2006, its re-badged equiv at Leslies, the TFP kit and that's it. (You can assemble the components but...it's still an FAS-DPD drop test)
I can't give you all the chapter and verse about why Ort systems or whatever are unreliable. If you store your kit in a cool, dry place where it doesn't get hit by sun, and don't let your chems get contaminated, they can last years longer than the "expires by" length of time.

If you want quick and easy, you can use Hach or Lamotte strips, but I don't recommend them as your only test system. The Hach Silver ones have TC, FC, pH, TA, CH and CYA. LaMotte has a similar strip. These are the two best strips out there (IMHO)

Carl