You've completely moved the goalposts; "testing automation tools" where your servers live for a few minutes then get destroyed is not the same as "a 24/7 environment". I didn't suggest renting servers to do ephemeral testing.

I only have experience renting physical hardware from Softlayer. They have built and imaged new servers for me in under 2 hours a dozen times, day and night. They also have a "xpress servers" line with guaranteed <2hr delivery. They also let you reimage your servers through their control panel or API; you don't need to have a new one built just to get a fresh disk image.