Sigint agencies hoard 0days and know they get "burned" by using them against a serious opponent that records traffic and can analyze and reverse engineer malwar

Sigint agencies hoard 0days and know they get "burned" by using them against a serious opponent that records traffic and can analyze and reverse engineer malware. If the 0day is useful against your own systems, you would hesitate to use it before your systems are patched. I think electronic warfare and ECCM systems can have similar dynamics. I always assumed (without any evidence) there is secret firmware or settings for these systems that will only be used in time of war and not used during training. I guess Israeli Air Force knows countries like Iran have the Russian hardware and personnel/training for dealing with the Elta gear that Israel exports, but I also guess the Israeli Air Force has secret sauce, maybe using the same hardware, that they don't export and use only for striking strategic targets, knowing each strike teaches the opponent something.