If you spend on the game to stay competitive it doesn’t end. There is always the next new HOTM or Event or Seasonal hero to chase, or you fall behind. What you spend now on the game will not ensure any kind of sustained longevity at the top without further spending later.
Spending to speed up the process, to shorten the grinding cycle, that gives you a longevity in playing but it will not get you to the top. Buying the VIP pass, cheap gem deals, being C2P. But that harbors no illusions of being at the top. That’s all about having fun. Just entertainment as opposed to competitive entertainment.