Until recently the bonds aka 'Training Agreements' were over 3 years, non reducing for 12 months from the date of final line check. This means the balance reduced on a pro rata basis over 24 months. So it is most definitely a 3 year agreement, not 4. However, I have it on very good authority that these have now been amended to start reducing from the date of final line check.
The whole 'Training Agreement' is a joke as far as I'm concerned. Ok if the company has invested something in you or a Type Rating but for Type Rated joiners the whole thing is a disgrace.
Cue the "you didn't have to sign it brigade"....