I know the boxes all say that you can keep it in over night if you sleep for 6 or less hours. But I sleep almost 10, and I'm not sure who would sleep for less than 6... anyway. Can I still wear a tampon overnight?
It is safe to wear a tampon overnight but put a new one RIGHT before bed and change it IMMEDIATELY after getting up. You may also want to up a size, to super-plus if you are bleeding heavy as that is a long time and you could get some leaking in 10 hours of sleeping.
You are sleeping for a long time, which is great, good for you! I wouldn't leave a tampon in for 10 hours, but a sponge or mooncup would be fine.