Just don't go all the way cold. Both SSDs and HDDs need to be regularly powered to retain the data stored on them over a span of years. As long as you occasionally access the storage volume, you're good, but if you're planning on leaving a drive untouched and unpowered for more than five years, the data might not survive even if the drive does.
For that kind of long term resilience, there's really only tape drives and optical.
Yes, but hardly because they planned on it. Don't use unpowered drives to store things! A safe bet is still a bet, data storage should not be a gamble.
I just recently went entirely HDDless in my desktop. I have a singular 10tb HDD external drive that I connect as needed, but I'm considering just moving it over to my NAS since all it does at this point is store dashcam footage.