Hello Final
Many years ago I was in the same situation as your self ( except the cadetship was as a radio officer in the days of morse code - god I feel old!).
But it can work well. I don't know what ships you'll be on, but I was deep sea on tankers and basically one six month trip paid for PPL, next paid for IMC, next for hours building, next for FIC (in the good old days before JAR/BCPL etc) - but you could come out of it in five or six years with a frozen ATPL and importantly no debts having had some extremely worthwhile life experiences along the way.
Your choice.....