I have my convergences set on all planes at 350 (except Me 262 and Hurri/Spit I).
I would advise against changing convergence back and forth between missions, or even against different convergence settings for the same weapon type on different planes. Each time you have to adjust your inner sight picture, and the benefits are probably quite limited under most circumstances (unless you are a very good shooter that can cope with that).
Often I read questions like "whut best conv for Pony... and whut for Jug?". Seems some players may think of convergences as a kind of magic trick... just find the magic setting and you will rake up kills like crazy. Unfortunately it doesn't work like that. A happy medium setting (default?) is probably the best all round. If you want to fiddle with your convergence settings, I'd suggest you film a lot of your combats and see at which distances you are actually shooting the most at, and adjust your settings from that individual perspective.