24 hours all the way to 5-7 days depending on the environment you're germing in. Just keep a close eye on them, multiple times a day and wait for it's little white ass to pop out. When the tap root is about 1/3 to 1/2 inch long, time to take it out of the PT and throw her in some soil👍. A lot of people and seed banks recommend a dark, warm cupboard and that works just fine...but using a germination heat mat will expedite this process. Lastly, do you do a seed soak prior to the paper towel or just full germination in the paper towel? Soaking a seed for 8-12 hours prior to the PT helps prime the seed with water and the germination process has already started before it hits your paper towel. I find the seeds move much quicker this way and in my first two grows I was able to start germing, sow and see a sprout in under 60 hours.
Hope this helped man. Good luck with the new life!!! And Grey is 100% correct. That paper towel gets dry...and you done shot yourself in the foot. Keep that baby moist and check often👍