This is a complicated topic.
Basically the original furlers (MEJ1) were a bit light for the boat. Bamar sort of admitted to this by offering A54 owners a deal on replacing them with more beefy ones.
I took this offer in 2018 when I bought our A54, although both existing furlers were still functional.
The original ones can last quite a long time but need much more maintenance then the new ones (EJF1). The new ones are also stronger (more torque).
What I do not like about the old ones us that the main bearings are designed in a way that seawater can enter because of play on the system that the seals are not able to cover. Also the MEJ1 has a belt drive and the belt needs occasional replacement. The EJF1 has a planetary gear system that is build quite sturdy and the bearings are quite strong.
So when buying an Amel 54 your problem will be assessing the state of the furlers. Ideally by taking them apart.
The new EJF1 do have a problem as well as the anodizing of the casing at the bottom is affected by the chrome bottom cover.
Some A54 had the furlers replaced by Reckmann. I think that is the best choice however eye-watering expensive. But the build quality is excellent.
I paid about 15k Euro for the replacement EJF1s (keeping the original foils) plus 4k dollar installation and new stays. Expect double the amount for Reckmann.
All in all I'm very happy with the new furlers they are very strong and smooth. I just need to do touch-ups on the casing every now and then.
Mind you there is also an electronics box below deck that controls the motor of the furler. I have heard may of them failed (including the ones on our Amel).