I think people talk about going two or three days over sometimes if temps are low, so hang in there.
We have high humidity here and I opened my incubator every day without mishap, so if you have high humidity in your room, I would pick an egg up and try listening to it, right next to your ear. Otherwise I'll search around - there was something in the forums about floating eggs on warm water and watching for tiny waves as indications of life. Dry climates, the risks will be different, so I hope someone else will advise you of the pros and cons of opening the incubator.
I have read of quite a few people having no success with their first hatch. Whatever happens, do try again! Get a breed with a reputation for toughness, like some of the bantams. I really recommend a breed you don't really like - birds you would almost be ashamed to give away. Now ones like that are going to hatch just to spite you, aren't they? And then you will be confident, and you can hatch something wonderful
ETA - I looked for float test posts. It seems people mainly do this with quail eggs because they are hard to candle. I, on the other hand, find anything near hatch date hard to candle - it's mainly darkness in there. So candle if you can, and here are a couple of quail threads if you're curious:
https://www.backyardchickens.com/forum/viewtopic.php?pid=3646969 (bottom post explains)
https://www.backyardchickens.com/forum/viewtopic.php?pid=3679500 (4th post from the top)