I can generally tell when it is time to toss it, it will start leaving a bump under the skin that takes a day or two to go away.
I'm injecting SQ in the belly using 5/8 needle. In my case, I'm thinking that would be one hell of a bump.
Now, I'd get nodules doing SQ T in the belly - using loads of >50ml and ASPIRATING.
I am also curious as to what would cause those bumps of yours... I've heard broscience say to put a couple of drops of HGH on a pregnancy strip, but not sure about that. Makes sense, just hard to convince my GF I'm buying/carrying around those tests simply to make sure my gear is good.
I'd definitely get "a look".