Second application of Visit Visa after conclusion of the same UK (6 months)

I applied for a 6 Month Visit visa to the UK in October 2016 and was granted a multiple entry 6 Month Visa. In my application my intended stay was of 2.5 months however, the training I was attending got extended and I ended up staying for about 4.5 months. I am back now and the 6 months Visa has expired. Another training has come up (scheduled 1 month from now) and this time for 2 weeks. Should applying for a short term 6 month Visit visa be violating the V 4.2 sections (states the applicant has not intended to stay as a Visitor as per my research).
- Should I apply for a long term visa for 2 years possibly to avoid this?
- Is there a time lapse after which one should apply for the Visa or an application for the same category can be done as soon as the current Visa expires?
P.S: I am being cautious so as not to unwittingly get myself a refusal.
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