Within the past few years, it’s become harder to convert airline miles into free tickets as the number of miles needed keeps increasing. The number of miles you’ll need will depend on:
Time of year
Distance
Popularity of route (the more popular the destination, the less likely the airline will offer award seats)
Fare class
Award availability
Some flights will charge as little as a few thousand miles, while others will charge as much as 100k+ points for a single seat.