I have been in the UK since September 2010. First as a PhD student on tier-4 visa, till 2017 September, then I switched to tier 2 visa from 2017 September till now. I have always had a leave to remain throughout the ten years, but I have been to my home country for vacation multiple times. I also have visited 5 conferences in USA, and been on tourist visits to Europe five times.
I was never out for 6 months at a stretch, but the eligibility for long residence allows only 540 days out of the country in the ten year period - does that mean without leave to remain, or regardless? To see if I qualify, do I need to manually calculate every single time I went out of the country, and add up all the days to see if they are less than 540? Is this how the Home Office calculates this? Any concession for PhD conference travel? Also should I wait for 5 years
on tier-2 if I am ineligible via this route?