Yes, but my point was more about the Soviet program of continuous improvement associated with it. According to your link, they stopped the assembly line at the

Yes, but my point was more about the Soviet program of continuous improvement associated with it. According to your link, they stopped the assembly line at the collapse of the USSR. It doesn't prevent them from upgrading the existing airframes like for the B-52, but it isn't a true rolling replacements/improvements program anymore like the F/A-18 [almost] is. Edit: Maybe the F-104 starfighter program would be another good example.