No way to predict how long it will last depends on how often you test and where you store it. Plus, you'll probably need to replace some stuff that you'll use up faster than others like the CYA test reagent. I typically just use an OTO/Phenol Red kit (yellow and red drops) for daily testing of chlorine and pH and use the big kit occasionally.

I can't say about the PS233. You can test with it and with the new kit and compare results to see if any of it is still good.