cross-correlation of a 15-minute file (presumably at 44.1kHz or 48kHz sampling frequency?) should be fairly fast. In pure Python:
import numpy as np
from scipy.signal import correlate
data = np.random.default_rng().normal(size=(2, 44100 * 60 * 15))
%time foo = correlate(*data, mode='full')
gives result
CPU times: user 4.74 s, sys: 1.15 s, total: 5.89 s
Wall time: 5.89 s
I don't recall off the top of my head how to time execution in Praat, but I just did this:
Create Sound from formula: "Noise", 2, 0, 900, 44100, "randomGauss(0,0.1)"
To PointProcess (periodic, cc): 75, 600
...and it finished in maybe 3 seconds. An available-RAM bottleneck is a good thing to check first.