The more you test, the better you know how your cat is reacting to the insulin. And that makes your life easier because dosing is based mostly on the nadir (lowest reading of the cycle). The nadirs can fluctuate on cats, as every cat is different (ECID), so it always a good idea to test enough to get to know your cat, and look for patterns in the spreadsheet that will help you with dosing.
Since I work for myself at home, I normally get a "mini curve" every day, which means at +3/+6/+9. At night, I will do at least a +3 and +6 because my guy is a diver, and I never know when his numbers are going to drop. If he's still dropping at +6 pm, I stay up later and test more.
As long as you are testing at home, and are using a meter where the test strips are affordable, the more you test, the more knowledge you will have.
Hope this helps!
Suze