The EPL schedule starts in mid-August and goes to the end of May. That's almost 10 months. Mixed into their schedule they've got FA Cup, Carabao Cup, Champions League and Europa League games. And that's just their club team commitments. For country, they have World Cup and Euro qualifying rounds (not in the same calendar years, but still...) that are scheduled within the EPL season. And when the EPL season ends the best players are off to play for their countries in World Cup and Euro tourneys.
It's a helluva busy schedule with no long period of downtime like other team sports. It's one reason why a lot of these guys have such a short shelf life and it's hard to find many performing at championship levels into their 30s. They burn out in their late 20s from wear and tear.