I was diagnosed at 47 initially T2 until autoantibody test showed T1. Probably a variant I was told. I do wonder how many slim T2s are in fact T1. My original consultant diagnosed T1 immediately but the next one refused to accept that and she would not do the tests either. Took me nearly 20...
Personally after 5 years I still love it. Of course we should all do what suits us. When doing finger pricks I was testing a lot anyway and I suppose that is because I want to keep tight control.
You can certainly have antibody tests when on insulin. Some doctors are reluctant to do them for some reason - probably cost.
It look me years to get a definitive diagnosis of type1. Eventually a supportive DSN managed to persuade my team to do the tests.