Define "long term"?

Long term is when your luck runs out.

This can be quantified to any degree of certaintly you like, the more certainty you require, the more bets you need to make before you arrive at the "long term". So I suppose to that extent "long term" IS subjective. However, the long term is most definitely not infinity, or even 1 million spins, so it's not as though anyone who believes that systems don't work is justified in requiring that the system pass the gazillion spin test (that's a

straw man directed at system deniers by system advocates).

If you're betting many numbers (say 24 or more) randomly (so that you have no edge), the house edge will overtake the variance after a couple of thousand bets (flat betting) with a degree of certaintly of 95%. This is about as many bets as you can expect to make and still be "lucky", assuming that your method has no edge. It follows then that if you continue to be in profit after this number of bets, you can be confident that you are winning for reasons other than luck.

For bets on few numbers, you need correspondingly more bets before getting into the long run. For a single number, the number is around 150,000.

Most system players are far too confident that they have something real, when in fact it's just positive variance (luck). Knowing when luck runs out for the quantity of numbers you're betting will give you a more realistic view.