im actually in your position right now.
I got promoted to D.III and im really comfortable where i am.
Yes, you do recieve much more money in the higher division, however, i feel if i continue to lose, i will not enjoy the game as much, and im trying to train a great player without throwing too many games to get minuites, and not losing gameshape.
I probably wouldnèt promote this season seeing as my player salaries are among the lowest in my league, however i wouldnèt go after promotion next season either as i do not want to lose all my games, and face relegation (which i hear is terrible) in D.II
If you want to stay put, learn the game, and get ready for next season, then do that, then you can have fun dominating your league next season.
Good luck