Is it good practice to include an optional CancellationToken parameter in my library methods?

For example, if my library has this method :

int LongOperation();

now i would like to support cancellation, but not force it on the user, and i would like to avoid creating a ton of overloads for every method

1) would defining this method as

int LongOperation(CanellationToken cancellationToken = default(CanellationToken));

be good practice?

2) i would like to support Async (TPL) and Synchronous support, but still allow it to be cancelled regardless.

would definition these methods be good practice ? :

int LongOperation(CanellationToken cancellationToken = default(CanellationToken));

Task<int> LongOperationAsync(CanellationToken cancellationToken = default(CanellationToken));

Any opinions / feedback would be appreciated.