EDIT:
You can test as much as you like. The critical thing is to test before every pre shot or "PS" as it is known here as well as the "nadir" especially while you are starting out. And since you are just starting you should be doing as many mini-curves as you can which are explained in the links I posted. Full curves are also good every now and then. One of your objectives should be to identify and capture when your kitty's "nadir" typically occurs [usually around +6 with PZI]. Once you get your info in a spread sheet then it will help others guide you better to testing at the right times.
Also I just posted some testing tips here:
viewtopic.php?p=141860#p141860
Not sure if that may help - but it's another beginner like you so there might be some applicable things to read in there for your situation.
Do you know the reason why the vet recommended 30 min? And only twice per day?
I'm not a vet [and I am just some random dude in some Internet forum] and I hate to disagree with your vet but IMHO, for the otherwise healthy cat, feeding twice per day is not the best strategy for PZI. PZI is a longer acting insulin and free feeding minimizes the effect of food on the curve. One may want to make sure their cat is eating at all before they give insulin, but if you know eating is not an issue then there is no reason to feed then dose. In H's case he has major appetite issues and he will just stop eating when I'm not expecting, but I don't not know what the issues may be in your case.
How does you vet feel about you home testing?
Further, normal cats should eat 10-20 small meals per day [SACN 4thed. Ch. 6 page 4]:
http://www.markmorrisinstitute.org/atta ... ts%20b.pdf
I thought I would also warn that traffic seems a little light in here the past week or so. So if you are in a pickle and need help immediately then do not hesitate to cross post in the main Health Forum.
BTW, Kelly's and Cindy's answer to your cross post question in Health was much better than mine, I just assumed you were giving insulin twice per day at this point?
What is your no shoot level at currently?