Checking requires a lot of training and shimush and is very complex. A few years extra at least before being reliable.

I wish the rabbonim and powers that be would regulate and endorse who is properly qualified for checking. Right now it is a joke, any one claiming to be a sofer can check your tefillin and mess them up. One tikun not done according to halacha and they are possul for life and no one will ever know!!! Not to mention not knowing many of the different complex issues that come up on checking. It’s serious stuff!