I can't agree more with Al's post.
The "answer" can be found in B31.3 book, however, too often overlooked. See below~
B31.3-2012
INTRODUCTION
The Code sets forth engineering requirements deemed necessary for safe design and construction
of pressure piping. While safety is the basic consideration, this factor alone will not necessarily
govern the final specifications for any piping installation. The designer is cautioned that the
Code is not a design handbook; it does not eliminate the need for the designer or for competent
engineering judgment.Understanding in a simple way is that the ASME safety Code is followed to prevent the built items from killing people but doesn't guarantee that the contractor following the Code will be a world-class company in the industry.
Engineering judgement is always necessary.
To my knowledge and experience, e.g., for elevated service temperature, repeated welding repair for several times of P No.1 steel doesn't harm too much as long as qualified WPS are followed. Creep failures can occur in carbon steel materials when subjected to longterm overheating while under stress. However, carbon steel materials are generally not used under conditions where creep is expected and the heat input of repair welding is far from making the steel and its joint longterm overheated. Same repeated welding repair to P No.8 stainless steels will result in excessive heat input that weaken the anti-corrosion ability of the steel. Common WPS's are not required by IX to be qualified by creep strength test or ASTM A262 test. That is out of the the safety Code, e.g. B31.3's scope of consideration.
For both the above steels, when dealing with low temperature service condition where impact requirement is specified, heat input is important and IX lists "supplementary essential variable" QW-409.1 to control the impact toughness of the welded joint. If repair was made too many times the owner may question the qualification of the WPS to make such repair since it was not qualified to weld with that level of heat input and the contractor can't guarantee the repeatedly welded joint still possesses the desired impact toughness.
I think ASME Code expects that an incompetent welder fails the performance qualification test by IX before (s)he is sent to the shop floor or to the site to repeatedly fail the RT. Have to confess that the actual condition of shop floor and site is not as ideal as that of the performance qualification test. But there are circumstances that some contractors fail to let the welders fail earlier.
Just some thoughts.
JZ