Subjective sometime, also depend on the customer situation, if they having some work done or just moving in then it's possible an idea time.... there is nothing worst than trying to rewire a house occupied with a ton of junk, I mean the customer furniture.!
If there are issue with circuits which requires investigation then you have to think, how many days will I be on this for and will it result in a satisfactory installation at the end?
also if the installation has been botched it make you think of all the other unseen botches hidden in the building,
if its old installation and had some heath Robinson work done over the years then I always suggest to the Owner they consider the possibility of the Rewire.
as the cost of me rectifying their problems will not guarantee the circuit from future failure especially if there are junction boxes hidden within the floor/ ceiling voids.
Never be afraid to recommend a rewire. there are very few installation I've come across which have require a rewire, but that does not mean I've not recommended it to the customer. To be honest most of them have a new CU and that can rectify a lot of issue.
Always Be Honest and up front and give the customer the Pros and Cons and let the customer make the decision generally get the best result.
