Soviets also often took up to a year to test and train on new craft before actively deploying them. They may have been in "units" but what kinds? They don't quite qualify them as "training units" like some German or RAF squads did, but you would have to know what squadrons and get a brief idea of what that squad was doing on those dates.
From early 44 onwards it was typical for a full regiment to be equipped with the first production batch for active combat duty under assessment.
Subsequent batches held back for modification.
Hence this first batch saw combat very quickly and was under assessment on the frontline.
Particularly true of the La7, Yak3 and Yak9U (although problems with the VK107 delayed the Yak 9U to a point where two regiments went to the front line under assessment)
Thru 41 to 43 production batches were immediately issued to front line units. LaGG, Lavochkin, Mig and Yaks being continually subject to minor changes as production quality defects were found or slight increases in engine performance/reliability discovered.
The best average life of any VVS aircraft in the GPW was 3 months............. less so in the period 41 to 43.