originally, there is around 20 cm of foil left at the top, above the swivel, with the original lashings (top and tack).
This means that in the foil's life, cutting off the bottom for new bolting can be done three times.
You may not know if the previous owners have already cut the foil at the base (for the same cause you face now). So, with your mainsail installed, and 10cm lashing between the swivel and the sail's top, you should go up the mast and look how much length of foil there is left above the swivel's top.
The cause of the bolts sheering the foil at the bottom is only using the furler (a lot!). Of course, some foils will last longer than other ones just because of the kind of use. If you handle the mainsail furler gently, the foil may last longer.
Be kind with your furlers and don't overload them (when the sail is fully in the mast, don't squeeze it by over using the furler). Don't try to adjust the mainsail under load.
You should drop the mainsail once a year to check the swivel (is it turning free?) as a seized swivel will add more load to the bottom bolt junction (and the motor and gear-box!!).
For those who have a short foil (already cut off a few times) and who cannot cut it anymore unless the swivel comes off the foil, the next step is to have a shorter mainsail made(at the luff).
Good luck and be kind with your AMEL, she will give it back to you...