Here is a consumer safety site for pens...

http://www.consumermedsafety.org/too...lin-pen-safety

Notice that even temperature changes may cause leakage with them, changing the concentration of the insulin itself.

I also have a concern about puncturing the membrane often.
It may not be designed for this and it may begin to leak or inject some air in there.

These devices are very complex, and somewhat like asthma inhalers. To get accurate doses each time, the device is designed a certain way for accuracy. If you alter its use, it may defeat the process and change the dosing.

This is why there are no generic pens, and few if any generic inhalers. It is just too tricky to get the engineering to conform to the product. It costs alot and requires specialist mechanical engineers to design these things.