I've germinated some stuff this way before. I didn't ever need to remoisten the paper towel - it's in the ziplock bag, so water shouldn't be able to escape. I've always taped mine to my window - I know they don't need light at that stage but I always thought they would do better if the sun warmed up the paper towel inside. Seeds like it warm from what I remember.

I would always fold the paper towel in half, nestle the seeds, fold it in half again so it was about the size of the baggie, and put it inside of there flat so I could hold it up and see through the paper towel if the seeds had germinated.

Couldn't give you a time window though... sorry! This is all anecdotal, I would still do a bit of research before going for it to make sure you get the best germination :)

I used this method which you described in your post on two seed of organic lemon and the result is in pic. both plants are 1 month old in the pic. It took 12 days to the seed to grow from normal seeds to 1.5 cm long roots. And then i plant the seeds with cute tiny roots in normal citurs soil with pre-added citrus nutritions. I put the seeds just under the soil probably with half a cm under soil and cover the pot normal plastic bag without making it air tight. But the seeds and plants never been in the direct sunlight. After one month i used fertilizer and it made the plants really happy. I will upload the updated picture of 1.5 month old plants tomorrow. I do not know about the process of putting seeds in the freezer but i read that many people use this process and i love to know difference. Good luck.

1.5 month

No on the freezer for citrus seeds. I put my seeds directly into the soil at about 1/2 inch depth; keep them moist and warm; and in about 2 weeks I get better than 90% germination.