Like you, I exercise most days. One slovenly day will not make much difference from my BG but when it becomes 3 r 4 days, my insulin needs noticeably rise.
For me, I think this is due to two things - the lack of exercise and the reason for the lack of exercise. Generally, I stop exercise because I do not have time or I am injured/unwell. The former is usually stressful mentally and the latter is a physical stress on my body.
However, as you mention, your diagnosis was only 18 months ago so you could still be in the honeymoon phase. My insulin needs slowly increased over 8 years as my beta cells slowly died off. So, your insulin needs may revert when restart working out but they may not, It doesn't matter. You need as much insulin as you need.