can any web hosting company guarantee that they will be up 100% of the time?
100% Up Time is impossible.
web hosting companies would not be able to make the guarantee of 100% up time because they do not have the products and backup features available to make that claim true.
Many of the web hosting companies that are available on the internet are small businesses with limited resources. These businesses do not have the massive server farms and software to be able to claim truthfully that they can guarantee that they will be up 100% of the time.
Due to overselling 100% Up Time is impossible.
There are many companies that have the ability to guarantee a better than 95% up time to their clients and make good on the guarantee.
I think there is no web hosting company that can truthfully claim 100% up time for all of their customers because one never knows what the future may hold.