from my experience, there are many factors that influence how long gamblers stay in gambling and most important thing is that it usually all depends on the desires and goals of each gambler.
I often place bets beforehand on slot game, poker and roulette. usually I spend 1 hour to bet on one of these games and it all depends on situation if losing streak I will stop rather than force a bet it better the budget I have to bet next day but if winning streak comes I once spent about 3 hours on a game roulette But as you said, the longer you gamble, the more you lose.
this assumption makes sense because the longer you stay in one of the games, the house edge will beat the gamblers.
but for now, after I feel bored of betting on casino game for at least 10-15 minutes, I feel bored and choose to bet on sports betting without having to waste too much time and choose to do a side job.
The time a gambler should spend while gambling differs per gambler. We know the elasticity of all our actions in life. A person who enjoys video games can stay up to 5-6 hours playing GTA. Gambling works the same way, I prefer a roulette game, it works in a way that I'd spend a good time playing the game, especially when on a good bankroll. Things do change according to the amount of money we own, but the games we enjoy on slots are very addicting because they require not much calculation. However, if a gambler on his leisure chooses to spend time and money gambling, he wouldn't need to bother about time, as he has some left. Hence, it all depends on the schedule of the gambler. Some may get tired along the line, it's true, as gambling takes up brain power and humans can easily get tired after spending time on screen. The players who can stay longer time like 6 hours, need to understand how to split their money while gambling.
The answer to Op's question depends on the amount of money the gambler is ready to lose while gambling. If gambling happened to be a free game that doesn't require money. Most gamblers will gamble at least 5 hours a day. But people may not get addicted to it. Somehow the money we spend while gambling helps in controlling the time, then facilitates addiction. It's hard to comprehend for a layman, but, while money controls time, emotions get affected due to the loss of money. The time a player spends gambling doesn't affect his thinking, but the money. So, some gamblers may have the time, yet no money to continue playing. And another gambler with lots of money to take him 5 hours on gambling, but no time to enjoy his habit. Those who get tired along the line and stop may have been gambling for days and need some rest.