They should last 10-30 years between service repairs depending on the climate you live in and the amount of use. If I did the repair, you should send it back to me as I give a lifetime warranty on repairs.
I don’t think that you can’ say it was not repaired properly if it has lasted 16 months since it was repaired. Even brand new electrical products only come with 1 year warranty. A repair implies that the faulty components were located and replaced but this does not mean that another part will not fail at some time in the future. As these units get older, the chances of subsequent component failure will be more common due to age but short of replacement of every component, this is something we have to accept.