A nice back horse is not "in a bowl", so that is not hollow, so that is rather straight. The saddle is perfect when it does not hurt the back of the horse, but the saddle must be changed when it damaged, it no longer goes to the horse, and especially when it deforms the back of the horse.
The duration of a horse saddle
It all depends on the originality of the saddle, but normally a synthetic saddle takes only 4 years up-to-date. Contrasting the leather saddles can serve you up to 15 years, of course if you apply the correct maintenance, that is to say a cleaning with each use. There are saddles of good quality that do not have to be changed but just to be adjusted. There are several workshops that work on the balance of a stool so just have a visit to have a good saddle again. Sometimes, you do not have to change your saddle when you buy a new horse, so check this option anyway.
The saddle that resists the most
The brands do not claim, but everyone still loves Antares, CWD or Hermes and others, indeed, the only problem with its brands is their price, so they are expensive. This longevity of the saddle also depends on the activity of the horse, because the used jumping saddles for sale do not require time for its use. In add, the activity of jumping requires an impeccable saddle, so a single fault can cause irreversible danger. A saddle of a very good mark, with good maintenance is guaranteed for life. The saddle of occasion does not need much of a spare, sometimes, it is enough to sew the padding and the saddle becomes again new.
Finally, the best saddle has no life, because all parts can change as and when they wear. But we can say that the life of the saddle is finished when the amount of the repairs gets exceeds.