I have a raw (unprotected) 3.7v LiPo cell. It's rated 4000mAh. It has the markings "HRDC 14.8wh 3.7V 606090P 20170528". Apparently 606090 is a number commonly associated with this type of battery, but I can't find a datasheet. What's a safe discharge rate?
I found some data here:
strangely the item listed there is not a 606090, but a smaller 592627 but the C ratio will be the same.
this may not be your exact cell but should be representative.
0.5C continuous, 1C peak
You should use a battery that has a current rating "C" that is rated for your load current. It sounds like you found a battery in a dumpster and are looking for a load for it to drive. If you use it in a Vape'r using a very high current then it might explode in your face or catch on fire.
Some of my RC model airplane Li-PO batteries are rated up to 70C and the weak ones are good for at least 20C.