Interesting. I have been Type 1 for 63 years, and generally been reasonably well controlled ( but not perfect). Like Caro2000, I was on Lantus, but was put on Tresiba a few years ago, being assured that the effectiveness of Tresiba could be up to 40+ hours, and that it generally effectively limited crashes in BS levels.
Personally, I have found as does Caro2000, that my BS spikes after c 4 hours of the evening meal, and I have therefore worked on the premise that far from it being effective for 40 odd hours, it actually starts to fall off in under 24 hours. I therefore take a few extra units of bolus insulin, which then tends to bring my levels fairly well back in line.
Every individual is unique I guess, though rather annoying that my nurse doesn't accept Tresiba can behave other than as it says 'on the tin'.
Hey ho