Thanks newcomer,
But I know about possibility to stop gaining experience in settings. It is not about if it is possible, it is about if it is worth. In fact - only mission reward which is valuable enough to wait is epic crafting instrument. ( of course I cannot know if some new type of reward will not be implemented ). Surely reward such bunch of epic items of very questionable ( dimplomaticaly said ) quality cannot be reason for waiting for such reward.
Once more time, many thanks for try to help me and also thanks to Xaoc for informations, Jany