The question you would need to figure out would be why tuckpointing would be the need of the hour. Signs of damp walls or cracks would point in the direction. You need to be aware that all these changes do occur due to breaking down of the masonry components. This could be due to age or seldom that could be the reason as well. If you carefully observe it could arise from small issues like leaky roofs or moisture vents to name a few.
You would need to observe the original damage to the mortar structure. If this does happen to be a lot harder than the brick you have gone on to use. It would be obvious that the mortar would have gone on to do the job itself. With the passage of time, the mortar will wick and fall. But the stone and the brick will not for sure. It does leave the wall in a good structural condition as well. You would need to take all these issues when you are about to start work.
When you are addressing steps for this issue the destruction of mortar would take place. So if you reappoint it will lead to a waste of time along with money. The worst part would be that more damage to the building structure can occur in comparison to the masonry structure.
If you go through the last few years, S mortar and N mortar are put to use normally. As they are durable they have gone on to become a lot popular. More and more companies began to produce them in pre-blend bags. The system of production went on to undergo a massive change at the same time. To field pre-mix mortars you can say that it was no longer the need. In the days to come, the market in this field was on the lower side. Instead of learning how to blend them the contractors began to pass the knowledge. In the days to come the concept of how to create blends was lost as well. It did go on to become a major problem that contractors were not even aware in modern times. You cannot say that what they went on to learn was not accurate. In a way, you could say that it was incomplete in all senses as well.
Most contractors are of the opinion that they could perform this operation. This can be done with the help of mortar mix. To match the aging of mortar they can go on to mix small portions. This would be a complet
ely wrong practice. To maintain the full ratio, the complete package has to be there. If you mix small amounts from this does work out to be an acceptable practice in any way. There are standards put forth in place that needs to be kept an eye on. Most of the bag does come with their own set of instructions as well.