It’s tricky to predict exact booking windows since prices depend on demand, season, and other factors. But generally speaking in Europe, low-cost carriers like RyanAir often have pretty stable prices, even close to the departure date. However, flights around holidays like Christmas can get pricier as you get closer to the date due to increased demand. My advice would be not leaving it until too late, especially since you have quite a strict schedule if you’re catching a flight to Nepal from Madrid. If you see a good deal, and it works with your plans, I’d say snag it. Safe travels!